I know many computer languages, but I’ve struggled all my life to learn a second human language. One of my problems is that I can’t stop trying to translate in my head. Just like Morse code, you need to understand things directly, not translate. But you have to start somewhere. One of the reasons metric never caught on in the United States is that it is hard to do exact translations while you are developing intuition about just how hot is 35 °C or how long 8 cm is.
If you travel, temperature is especially annoying. When the local news tells you the temperature is going to be 28, it is hard to do the math in your head to decide if you need a coat or shorts.
Ok, you are a math whiz. And you have a phone with a calculator and, probably, a voice assistant. So you can do the right math, which is (9/5) x °C + 32. But for those of us who can’t do that in our heads, there is an easier way.
Field Expedient
Most of us can’t multiply by 9/5 in our heads. But 9/5 is very nearly two. So if you double the Celsius temperature, you are halfway there. Of course, the number will be too high. But to make up for it, instead of adding 32, just add 30. For weather temperatures, this gives you a ballpark estimate. For 0 °C, you get 30 °F instead of 32. For 20 °C, you get 70 °F instead of 68. For 35 °C, you get 100 °F instead of 95. All close enough.
If you want to flip the error as the temperature goes up, you can remember to add 25 instead of 30 if the temperature is more than, say 25 °C. Then 35 °C gives you 95 °F on the dot, although other temperatures will still have some error, of course.
The error gets worse as the temperature rises, but it has to get fairly high before it gets useless. For example, my AMD CPU is currently at 48 °C. Using the +25 estimate, that’s 121 °F, instead of the correct 118. But maybe it won’t help you set up your metal smelting furnace.
Other Estimates
This is a useful way to embrace metric. Find rough estimates for units you deal with. For example, 2.54 cm/inch is not the easiest thing to apply. But if you remember that 5 cm is about 2 in, that works well. So a 160 mm rod is 16 cm. If you think of that as 3 x 5 + 1, you’ll know it is 6 inches plus an extra centimeter. The right answer is about 6.3 inches. Not close enough to start cutting things, but it does give you a feel for how big a thing you are talking about.
If you lived through the time when gasoline in the US went from less than $1/gallon to over, you might remember that many gas stations switched to liters because the pumps couldn’t be set for a dollar. The reason is a liter is very nearly a quart, and there are four quarts to a gallon. So 12 liters is practically 12 quarts or 3 gallons. This turns out to be very close.
Kilograms and kilometers are a bit trickier. The right way to imprecisely convert kilograms to pounds is to multiply by 2.2. But a nice mental math trick is to double it. Then remove the last digit and add the rest back in to the whole result. Then put the last digit you removed after the decimal point. So 8 kg would be 16+1 (throw away the six) or 17 pounds. Then put the 0.6 in for the correct answer of 17.6 pounds. Of course, the conversion factor isn’t exactly 2.2, but that’s what most people use anyway. If you are trying to be scientifically accurate, none of this is going to help you.
The factor for kilometers is roughly 0.6 miles in a kilometer or 1.6 km/mile. If you halve the kilometers, that will get you a fairly low estimate. So 35 km (21.7 miles) is easy to guess as more than 17.5 miles. That’s a pretty big difference, though. But if you then add 10% of the 35 back (3.5) you get 21 miles which is close.
Advice
I’m not trying to say that these rule-of-thumb tricks are good when you need an exact answer. But they are handy when you simply want a gut feel over some measure. Over time, you’ll just naturally know that 35 °C is summer-weather hot and you need more than a coffee mug to hold 3 liters.
Do you have a favorite fast conversion back or forth from metric? Share it in the comments. Americans love their strange measuring system. Turns out, some of the reasons we didn’t get metric was due to pirates, as you can see in the video below.
Featured image: Wood thermometer on white background by Marco Verch under Creative Commons 2.0
You are too optimist, most Americans aren’t even able to spell “Celsius” correctly (Selsius), let alone doing math from “Harry Potter” units to SI / IS :)
Sure, it’s spelled C E N T I G R A D E.
J/K
Kelvin degrees are centigrade as well, so no, avoid ambiguous definitions.
C=Celsius not Centigrade
Kelvin is not in degrees. It’s just Kelvin, nothing extra. The “degrees” in Celsius is a reference to diving the temperature difference between freezing and boiling water into 100 parts, but there is no such division for Kelvin.
Wrong. This is the same difference as for Kelvin. Well, actually Celsius is defined in terms of Kelvin, shifting Kelvin up from absolute zero to the triple point of water.
(but you are right, it’s wrong to say “degrees Kelvin”)
That’s just a convention which is in place from 1967
https://www.bipm.org/en/committees/cg/cgpm/13-1967/resolution-3
More matter of pointless nitpicking than a logical/practical motivation.
Now if people understood what a kelvin degrees was before 1967 I can’t see why they can’t understand now.
“More matter of pointless nitpicking than a logical/practical motivation.”
No – the distinction’s important. A degree indicator indicates that it’s a scale reference, but not absolute or natural. Graded steps between two points, not absolute – hence “centigrade” – 1/100 of the total range. It’s the same logic as for why angles in degrees make sense to call degrees. They’re a relative measure, but you can’t put them in things that want natural angles (radians), like trigonometric functions.
Temperature deltas don’t matter between kelvin and degrees Celsius, but multiplicative conversions and temperature ratios do. The Stefan-Boltzmann constant is 5.67E-8 W/m^2/K^4, no degree symbol for a reason, and I can tell you for a fact that people have screwed that up by forgetting you can’t use celsius temps there in ratios of power emitted.
Bob and Doug McKenzie solved this 45 years ago. Double it and add 30.
good luck with your 180 deg C oven recipe that you just set the temperature 30+ degrees too high
Hose off! ;-)
“aren’t even able to spell “Celsius” correctly (Selsius)” Challenge. Sounds like nonsense.
This article is for people who don’t know their times tables but still expects them to do multiplication.
All one needs is 0,1, and 2. 0 is ice, 22 is nice, 100? Not sure, stick your hand in it and let me know. I will also allow 3 because every ruler proclaims 30 cm per foot. And of course 6 for longer distances.
“The right way to imprecisely convert kilograms to pounds is to multiply by 2.2. But a nice mental math trick is to double it.” It’s adorable that you don’t notice that “the right way” is to do the “nice mental math trick”. Twice.
9/5 vs. 1.8: I must have been out the day we learned our 9/5 table, but multiplying by 1.8 is really just multiplying by .8 which is really just multiplying by 8. If 9/5 is easer for you have at it.
Anyone who follows this article’s advice just doesn’t value their time.
Actually, multiplying by 1.8, i.e. 9/5, is doubling less one tenth of that. Works for all C to F conversions. 1234 C gives 2468-246.8 or 2221.2. Adding the 32 offset gives 2253.2 F. Easy to do mentally, even for negative values. Absolute zero is about -275 C? Double (-550) less 1/10 (55) gives -495; add 32 offset gives -463 F. Piece of cake.
If adding 32 is a nuisance, you can convert C to F and F to C with the identical equation with one constant inverted: C= 5/9* (F+40) – 40; F=9/5 * (C+40) – 40, since -40F = -40C. Some find that easier, some don’t. Take your pick!
Came here to share this trick.
Convert C to F, as an example 20C ->
20*2 = 40 (this is the only multiplication you need to do, the rest is addition/subtraction.
40 – 4 (40/10; move the decimal) = 36
36+32 = 68.
It’s perfect; you don’t have to do any silliness with adding 25 or 35 or whatever.
Well.. since the inventor of the scale Anders Celsius spelled it with a C I would argue that that is the correct spelling (https://en.wikipedia.org/wiki/Anders_Celsius)
Obviously Celsius is the right spelling, but just look even on this very blog how many Americans write Selsius
None
I have never ever seen anyone attempt to spell it that way. Everyone at least knows that the symbols are “F” and “C”, so this sounds like a straw man argument. It’s just as likely that the rest of the world can’t spell fahren-….farenhite….faerunhight….the F one…
A flamethrower sounds the same in every language.
“0.6 km/mile or 1.6 miles/km”
Are these units upside down (reciprocal)?
Being American, I had to make one mistake. The math is write, I just flopped the numbers in that sentence. Doh.
“I had to make one mistake. The math is write”
this is epically hilarious, thanks Al
I thought you might appreciate that.
It’s a shoutout to Muphry’s law, eh ;)
(yes, correct spelling, look it up)
From UK Kelloggs Cornflake boxes in the 1970s:
“Two and a quarter pounds of jam weighs about a kilogram”
“A litre of water’s about a pint and three quarters”. But UK pints and gallons are not the same as US pints and gallons :-D
Before car speedometers went digital in the UK they were marked in both mp/h and km/h. So easy to notice and remember that 50mp/h is 80 km/h.
Everywhere except the USA:
“A pint of water weighs a pound and a quarter” (or 20oz.)
A pint’s a pound, world around!
60 is 100 and 100 is 160. The rest, you can interpolate. :)
OTOH, when the speed limit is marked in miles/h or km/h, you usually end up with a car with a speedometer marked appropriately as well. And they’re marked in both for the US/Canada market as well.
You just have to remember that the units have changed. (True story: 19-year-old me in Montreal…why is everyone driving so slowly, it’s an 80 zone?)
I don’t see any point in “embracing metric” for household temperature measurments. Meters are great because all the units are powers of 10, and most scientific formulas are much cleaner. But for household use this does not matter at all. Now I get if you’re already using metric for everything else, why have a seperate scale for household temperatures, but in the US we’re already on a mixed system, so that doesn’t really matter either. Once we’re off of gallons, miles, inches and feet, then sure.
I’m actually not sure why we’re still so stuck on SAE. The old argument was that all the tooling is SAE, but now a huge amount of that is made in China and other metric countries anyway. Almost all modern machines support metric units. Just a matter of buying some new screws, bolts and drills.
“I get if you’re already using metric for everything else, why have a seperate scale for household temperatures”
It’s a silly argument anyway – metric already has multiple temperature scales, and the Kelvin/Celsius difference has caused problems with people who forget that temperature ratios only work with Kelvin or screw up the conversion.
And temperature itself is bull anyway – it’s not a real unit to begin with. In modern SI, it’s just a flat-out definition, it has nothing to do with water in any way shape or form anymore. 1 Kelvin is ~13.8 yoctojoules. Personally I prefer an indoor temperature of around 4.06 zeptojoules, but I understand people might prefer as high as 4.09 zJ. Anything under 4.03 zJ is just crazy, though.
People invent new scales all the time when it’s convenient. The scale doesn’t matter – the definition does, and Fahrenheit is defined based on SI units just like Celsius.
“I don’t know how hot or cold 80 deg F is outside” is a waaaay sillier than “how bad is 26 deg C”. Because with Fahrenheit, climate is basically “0 is too cold to be outside and 100 is too hot to be outside.” Interpolate between.
In household terms the great advantage of metric units is the conversions. Powers of 10, or more usually 1,000 between units and it is often relatively trivial to convert volume to mass as 1l of water masses 1 Kg. Fundamentally though not having 2 different sets of units will simplify the whole world, reduce costs and eliminate a huge swath of conversion issues. As the imperial units are now all defined in terms of the base SI units, the reality it is just hat everyone is used to. IT is a long hard road but the UK went metric in the 70’s. I grew up dealing with both imperial and metric units but by the time I was at university imperial units had basically vanished and the few remaining ones are fading as kids grow up and old fogies die off.
As a Brit living in the US I get particularly annoyed about units with the same name – fluid ounce and pint, I am looking at you- that are different between UK imperial units and their US equivalent.
yeah people always say the power of ten thing but to me the beauty of metric is 1mL = 1g = 1cm^3. ties everything together neatly using the density of water in the nice normal condition of “roughly similar to what’s on your table”.
more concretely, 1 Joule = 1 Newton * meter = 1 Watt * second = 1 Coulomb * Volt. 1 Ampere = 1 Coulomb / second. it’s just so handy having all these actually-different units clearly related to eachother.
the only one metric really misses is 1 calorie = 1 degK / gram = 4.184 Joule. (calorie is not metric) but you can’t win em all.
people don’t seem to actually use the power of ten thing anyways. like, people love 1t = 1 tonne = 1 metric ton = 1000kg. i’m usually the only one talking about Mg megagrams.
It’s not even to powers of ten. It goes 1, 10, 100, 1000, and then everything bigger is 1000 times more. Same thing with smaller things. 1, 1/10, 1/100, 1/1000, and then 1/1 000 000 etc.
Though of course the English speaking countries that were the last to convert to metric tried to simplify it by saying it’s only about factors of 1000, so they dropped the deci-, deka-, hecto-, and tried to get rid of the centi- prefix to pretend there’s only milli- and kilo-.
“and then everything bigger is 1000 times more. ”
Well, now, at least. The 1E5/1E-5 prefix was dropped in ’60. God knows why we still have the 10 prefix.
“it’s just so handy having all these actually-different units clearly related to each other.”
They weren’t originally. Volts, amps, watts were electrical units. Around the turn of the 20th century was the push to unify the mechanical and electrical units, but it requires tossing the old CGS units (dyne, erg) because that would have forced the EE types to change and lol.
It’s the reason why SI units are weird and mix base units (meter, kilogram, second) – only way to make power work.
Get rid of the calorie. It is broken since people started saying calorie when they meant kcal.
“It’s not even to powers of ten. It goes 1, 10, 100, 1000, and then everything bigger is 1000 times more.”
Do you see the letters that are coming out of your fingers? What is 1000 a power of?
“What is 1000 a power of?”
10,000 is a power of 10, too. What did myria- ever do to you that you decided it had no value?
The point was the arbitrariness of what powers to use. You could also argue the arbitrariness of naming the prefixes, too – why are you asking people to memorize like 20 different prefixes they’ll virtually never use?
At one point, instead of prefixes, people suffixed the unit with the number for the power (or prefixed with the ordinal number if it’s a negative power). That’s a massively more rational system (only two things to memorize!) but tell people to use “sixth-gram” instead of microgram and they’re like ‘that’s ugly.’
I remember in school, when we were learning the units, it was just moving the decimal point by one digit. Meter, decimeter, centimeter, millimeter. Then later when we’d deal with micrometers and nanometers in physics and science, it was easy to make the error that a micrometer is 1/10th of a millimeter when it’s 1/1000th of it. Trivial errors like that lost so many points in exams.
It wasn’t the same issue going the other way, because nobody used deka- and hectometers. It was just meters and kilometers, so the difference was a factor of 1000 going up, but factor of 10 going down, except at some point it turned to factor of 1000 again. Completely arbitrary and confusing.
It’s no wonder some countries like Australia are trying to eradicate all the units that aren’t a factor of 1000 to each other, but then they’d be losing useful units like the deciliter or the centimeter.
Unless your tap delivers chemisty-lab-analytycs-grade pure distilled water then this 1L = 1kg is bullshit. Weight will differ due to various salts, heavy metals and other contaminants present in the water.
What are significant figures?
I’ve never heard of them.
Technically even lab grade wouldn’t be. It’s not the definition anymore.
It’s the intent, just like the meter was intended to be related to a quadrant, Celsius was water-related, and the permeability of free space was 4 pi E-7. None of them are exactly true because the definitions are no longer based on simplistic things like that.
The only thing that was really key about the metric system was tying weight (mass) to water volume. That broke a ton of fraud and democratized weight measures, which was super important. (And then the standardization of all measures, but weights were the important one).
The power of 10 thing is massive red herring. First, it’s not true: squares and cubes and such mean you’ve got irrational values floating around with volume/mass, and seconds/minutes/hours breaks everything, of course. Kph to m/s is not a power of 10.
Plus, just look at the prefixes. No one uses them outside of a few (relative to the total available). No prefix bigger than kilo is used for grams unless you want to sound cool. Europe uses “million metric tons” even though the metric prefix would be way shorter.
The metric system is great because is standardized the measures in physical properties. That was the key. Grams are just objectively better. The meter won because they figured out how to make a more stable bar, even though the way they came up with its length was epically stupid and dumb. And they came up with the prefix system because it made them sound more technical and less like the “common folk” (seriously not kidding).
I’m seriously amazed people think that it’s the units that cause problems. It’s not the units. It’s that you’ve got multiple standards bodies. The units have exact conversions between them. It’s not about “1 set of units” – you need to create one standards body, and as the old XKCD comic says, you have N standards, you want to replace them with 1, you now have N+1 standards.
Or you’re a drug dealer. They seem to like it for some reason. Hector is a common name that comes up quite often.
Hectoliters are used for beer and wine barrels. Agriculture uses kilograms per hectoliter to measure grain weight. Etc. They have their own niche uses where they replace the older “bushel per barrel” measures.
“They have their own niche uses where they replace the older “bushel per barrel””
Yeah, once again bringing back the XKCD comic – let’s get rid of this arbitrary niche definition and create a new arbitrary niche definition.
It’s actually funny, because I’ve seen more of a unit mess at European grocery stores than US ones. If I go buy lunchmeat in the US, it’s always in pounds (or in small amounts, just ask for the number of slices). Half pound, third pound, one pound, etc. Obviously ounces are still around for stuff by weight, but it’s way less comon – it’s just fractional pound anymore.
In Europe, I’ve seen grams, dekagrams (wtf let the two worst SI units die please), and kilos, depending on what store/country you’re in.
The idea that there’s no unit confusion anywhere except the US just cracks me up. People use what they’re comfortable with. Always have, always will.
Decagrams ? Where have you seen that? I have never seen that anywhere in Europe.
“Decagrams ? Where have you seen that? I have never seen that anywhere in Europe.”
Grocery store in Hungary. Shows up in a few other countries as well, I guess, but that’s where I’ve seen it.
The European I was with at the time was like “that’s just weird,” which cracked me up. “Everyone use the metric system” “OK” “Not like that!”
“Kph to m/s is not a power of 10.” Science has decided not to use hours or fortnights as units of time, Strawman. Number km/hr is easily convertible to Number/3600 km/s. Library books are also not a power of 10. The list goes on and it doesn’t matter.
“Science has decided not to use hours or fortnights as units of time,”
LOL. Science uses whatever the heck is common and easy to use. No one cares what units are used so long as their standard is derived from SI. RPM, kWh, lightyears, degrees per hour, liters per hour, etc.
There’s a reason why you learn “there are pi times 10^7 seconds in a year” in first-year astronomy.
In the shop and home, the shortfall of SI is in fractions. 10 is commensurate with only 2 and 5. The 12 to a foot of US Customary is commensurate with 2, 3, 4, and 6, providing a wealth of rational numbers, and rational arithmetic is exact.
There is also the issue of over-syllablizing. The customary units all(most) have 1 syllable names that are impossible to confuse with each other, saving thousands of man years of YouTube time.
Wait what. The whole problem with freedom units is all the damn fractions. An American architect will specify the scale of their drawing with something like 1/32″=1′. Who the hell knows what that means because it’s not just 1/32 scale. There’s another factor of 12 thrown in there. At least decimal feet drops those damn inches and fractions.
“IT is a long hard road but the UK went metric in the 70’s.”
In the U.S. “IT” means “Information technology”. What does it mean in the UK?
-20 is too cold to be outside and 40 is too hot to be outside, interpolate between
wow, those seem like interesting temperature points, maybe we should make a scale based on that and put those at 0 and 100
Interpolate between what?
FTFY: -5 is too cold to be outside, 28 is too hot to be outside.
Fahrenheit picks some arbitrary points.
That said, using “0F=too cold,100F=too hot, interpolate” is stupid anyways because 50F is not “perfect temperature” and nobody in all of eternity will ever think “69F? That is almost 70% Way Too Hot” and find it useful in any way or form lmao.
It works like grades. 50% of the way is still failing. You need ~70 to be average. :)
lol, this is literally how I explain it to people
Clearly you haven’t been on the internet enough, because 69 degrees is “Nice!”
Uhm, we use subdivision with Celsius you know, when I check the weather it’s 26.3℃
And I just checked and the US weather uses whole numbers it seems. Odd, but it explains your confusion.
Ignore that comment, it went to the wrong person’s thread.
I definitely think of room and weather temperatures in F but for anything hotter than that which burns by touching it, it’s in C. It changes over around 140 F or so. I definitely have a “feel” for temperatures from about 180 C to 400 C (from 3D printing and soldering), but I have no idea what that is in F.
Come to think of it, that goes for other measurements too. Liquids smaller than 1 cup are in ml for me, anything larger than 2 liters is in gallons. Anything smaller than a pound is in grams. Anything longer than a few thousand feet is in miles, everything smaller than 2 feet is in mm, unless it involves feeler gauges, micrometers, manual milling machines, thin sheeting, or radial lathe dimensions, then it’s in thous. Axial lathe dimensions are sometimes in mm. Laser cutter, PCBs, 3D printing, and CNC milling are always mm.
hahah i definitely live in this same universe that you do
your remark on liquids smaller than a cup reminds me…i do use floz sometimes but imo 1floz = 30mL = 2Tbsp and 1Tbsp=15mL, 1tsp=5mL. even the ridiculously unmetric measures floz, Tbsp and tsp, i understand in relation to mL.
You remind me that U.S. luthiers* use mm for measurements, (so I was told by a l. friend). *They make and repair bowed and plucked instruments such as guitars and violins.
“Most of us can’t multiply by 9/5 in our heads. But 9/5 is very nearly two.”
Yeah you can. 9/5 is 2*(1-0.1). So double it, and lop off 10%. Which is just sliding the decimal point back and subtracting. 24 deg C becomes 48-4.8 or about 43, add 32 and hey looky.
The scale difference between Fahrenheit and Celsius is 180/100, which is a useful conversion to know anyway.
Very similar to the 2.2 trick I mention later for kg. However, the double+30 is easier for non-math types and is quite good for temperatures normal people encounter.
Innumerate.
The word is ‘Innumerate’.
Like ‘Illiterate’ but for numbers.
Don’t use soft language to preserve the feelings of the dumb and lazy.
Unless you’re trying to F them, of course.
Should go without saying.
So you count being able to do multiplication tables up there with literacy? I’m definitely math minded but simple arithmetic and multiplication is not something I care to hold in high regard. I even check myself with a calculator on the dumbest of calculations, because something as simple as flipping a sign can result in hours of rework or at the worst case a lawsuit. Rather ensure I’m right the first time.
So what?
Spell check is a thing too.
Being able to multiply perfectly in your head is comparable to spelling perfectly.
A trick that only the quarter smart care about.
Knowing how to count == Knowing you ABCs.
Add, subtract == Writing your name.
Multiply, divide == Writing a sentence.
HS algebra == Formulaic four paragraph thesis.
HS calculus == Fully numerate.
For livable temps, yeah. For cooking temperatures, less so. Using a temp of 390 F instead of 350-360 when a recipe calls for 180 C is kindof noticeable. Double it (360), lop off 10% (about 320-330), and add 30 (about 350-360).
You just have to know “you’re about 10% too high” and then it’s easy to think if it matters.
For chicken I’ll roast it anywhere from 350F to 400F. I take it out when I think it is done. Zap it in the microwave if I think it’s a little suspect. Maybe actually measure it using whatever scale I happen to have handy, most meat thermometers have recommended internal temperature printed somewhere on the packaging.
For baking, it’s extremely critical to get all measurements in place to have consistent results. Dry ingredients by weight. Must get the correct ratios for liquids. Even a square pan versus a circular makes a difference. It’s tough and I can only bake a few things with any confidence.
At the old iron foundry where I used to work, temperature was incredibly critical. We used Fahrenheit in most places except in the spectrometer lab where we used Celsius. And when I say “most places” we not only checked the melt temperature in the Disa, but we also had to check the sand temperature in the inlet hopper for casting.
I well recall learning 5/9 and 9/5 in school, but teachers did not explain why they worked. Some decades later, I subtracted 32 from 212…
There are so few good explanations out there for where the Fahrenheit scale came from. It’s frustrating because even when people describe it, it’s usually “well, we don’t know exactly why he did…”
I mean, yes we kinda do. If you’re building a weather thermometer for temperature from scratch, a Fahrenheit scale thermometer is easier to build.
This might seem weird, because you’d think “boiling/freezing water” is easy to calibrate, but it isn’t – your thermometer is now 2x bigger than you actually need for weather. And in addition, marking divisions between 0 and 100 is awkward. You can split it in 2 for 0-50 and 50-100 easily, but after that, making multiple precise subdivisions is awkward.
Fahrenheit was actually a very smart instrument maker, which is why the scale was popular – they were cheap and precise. He went through a bunch of different iterations, but calibrating at brine and ice for 0-32 meant you could build reference markers from splitting multiple times since it’s a power of 2.
And then repeating that same set of reference markers twice just a few times gets you all the gradations you need for weather. It’s funny because most people defend Fahrenheit by saying “well it’s 0-100 is basically all the useful weather temperatures.” And it is. Because that’s literally what it was built for.
I’ve come to the conclusion that human brains function more like look-up tables than like calculators. That means that the more proficient you get at multiple systems, the more likely you are going to pull from your noggin-powered database that “75F” equals “25C-ish” equals “nice” equals “t-shirt”.
The same happens with dimensions.
– 1/8″ equals “fat 3mm” equals “wood screw pre-drill size” equals “the bit usually in default in my drill”
– 1/4″ equals “visually clearly bigger than 5mm, and no one uses 5mm bolts much”
– 5/16″ equals “a fairly chunky bolt but not quite impact driver territory” equals “what ruins M8 threads”
– “it’s serious business” equals “3/8” equals “M10-ish”
It’s also the reason why certain languages like Finnish with lots of stacked conjugations and cases, are so hard to learn. They are thought grammatically (using logical sequences of grammar rules) but natives speak it using pre-structured blocks. They don’t conjugate a sandwich of rules in their heads. And that’s why it feels to learners that they are rendering on a CPU, while the natives are cheating by Nvidia.
Not in the simple cases, but they can.
https://en.wikipedia.org/wiki/Polysynthetic_language
“I’ve come to the conclusion that human brains function more like look-up tables”
Close. They’re relational. They can’t store facts. We’re not computers. We store relations, not information.
That’s why it’s so hard to teach – you want to present it as a list of rules, and concrete information, because that’s how you grade. Except it’s not. It’s recognizing concepts in relation to other concepts. In math, it’s recognizing that addition is to subtraction like multiplication is to division like powers are to roots like exponentiation is to logarithms, etc. etc. etc.
It’s also why I don’t understand people being bothered by multiple unit systems. Your brain loves having new concepts it can attach lots of references too. It does it all the time. City blocks, days, months, seasons, school years, work lengths, etc. It doesn’t think in powers of 10, it thinks in “dafuq concept do I have that’s close to this thing.”
The biggest issue with imperial/metric is the tooling difference, but that had nothing to do with the metric system: it’s an international standards organization problem, and hey, it ain’t the US’s fault that Europe took so damn long to have manufacturing standardization.
I mean, I can’t think of any reason why Europe wouldn’t have been able to all agree on something in the early 20th century.
“Close. They’re relational. They can’t store facts. We’re not computers. We store relations, not information.”
That’s either wrong or a lie, your choice because direct perception and I remember my home address so right there it’s disproved, by experience. I can do it with reasoning if you insist. Beginning with “relations between/among what?” At most you can assert that you are not a computer, HAL. You cannot speak for “We”.
“Can I remember a fact” is not “my brain stores facts.”
It’s not wrong – it is harder for people to remember bare facts without relational anchoring. Not impossible though, if the facts are small enough and repeated often enough, and you don’t need to retain them with any great fidelity for too long.
That’s how you can remember a phone number, but to remember a deck of 52 cards you basically have to invent a story that goes with each card. Otherwise it takes you forever to memorize it.
Exactly, and this is easy to harness.
One day I figured out that I can look at a UPS tracking number, divide it up into 2 or 3-digit chunks that relate to something, usually an area code, a ZIP code, a date or some other token, and just effortlessly memorize it that way. It usually goes something like:
“the usual start string”-New York-Amsterdam-My shoe size-my ex’s license plate-the temp in Death Valley when I visited.
Something short with a rhythmic cadence like “york-dam-shoe-plate-death” you can easily retain in your brain for half a minute. And then you reconstruct it back into numbers for, say, typing it into a website.
Right: I didn’t mean you can’t store facts, I meant it doesn’t store them. You can shoehorn it into storing facts, but only if you link it into other things.
Think of fact memorization like brain hacks. It ain’t designed to do it, but when has that ever stopped us?
No, you can store raw facts just fine. You only need one link: what the fact is. You don’t have to make up stories and associations to remember your mother’s phone number – you can simply think “mother’s phone number” and the number will come up if you’ve repeated it enough times.
Relational storage ensures robustness and ability to recall and recombine information with fewer repetitions and shorter exposure, but good old rote memory works just fine as well.
The brain learns raw facts much like how you learn to dance. The motions of your legs and body are arbitrary and you’ll be clumsy at first, but when you repeat the motions enough times it becomes fluid and exactly repeatable.
Without the ability to retain raw facts, we could not absorb any foundational knowledge to be able to form relational knowledge. If all memory is just references to other references, we would be doing syntax but not semantics and our thinking would not be grounded anywhere. Some would say we wouldn’t be thinking at all, since nothing would truly mean anything.
In other words, the mental categories and references you have are formed at some point of your life when your brain picked up a repeating pattern and decided to keep it without knowing what it is. The fact that this pattern is called “Red” or “A ball” came later when you learned other stuff and started to think abstractly.
Just disagree. Rote memorization is still relational: you repeat it so much that there are so many other things going on in your life that it links to.
“I’ve come to the conclusion that human brains function more like look-up tables than like calculators.”
You make a very good case for this, I never thought of it that way. While there’s often a little calculation involved to refine the results in a particular circumstance, what is a multiplication table other than a lookup table? Bravo!
Just like stringing together commands into a batch file isn’t really “coding”, speaking a language natively is not really actively using grammar, at least most of the time.
Often, when natives are asked how a certain part of a language works, you often get “I actually don’t know, that’s just how we say it.”
I think it is the same reason why languages with lots of irregularities in their verbs or elsewhere don’t require more effort from native speakers than a more straight up, “mechanical” language does. You just pull the irregular form from your database and wouldn’t even notice it is irregular.
Yeah, it’s the same way that words pulled from other languages get connotations and ‘special grammar’ – they get pulled in with a certain context, and that context gets ‘baked in’ to the usage of it. In English, you use the Romance-derived words to sound fancy, you use the Germanic words to sound more common and harsh, and you end up modifying them based on their original languages. Hence the reason parents spend so much time correcting “-er/-est” vs “more/most” in English.
Linguists can point to the reasons for it, but in everyday use it just “sounds wrong” because of the context you’ve always heard it in. Which often leads to issues between people using a second language, because they’ll grab cognates without realizing the unwritten usage rules. And often eventually those “wrong” usages get turned “correct” as the social context fades.
Whereas 5mm equals 10. 10 what? Just 10. That, is a size 10 UNF (32tpi) screw is so close to M5 that you can use one in place of the other without jamming up the threads.
You’re a mile deep in the long tail with this one. Of course this and even more obscure standards exist. But if you encounter a “yay big” bolt, say 1/4″-ish, outside of specialized industries/applications, say the Home Depot bulk fastener section – which is invariably a mess – you’re going to be able to eyeball it 99% of the time.
It’s even easier in Europe. If you go to a store that sells hardware by the metric pound, you can eyeball all the sizes from M3 to M12 with one hundred percent hit rate. Everyone knows what an M4 bolt looks/feels like, and you’re never going to confuse it for an M3 or an M6.
Famous last words.
You realize there are multiple thread pitch standards for many diameters?
I see two or more round trips to the BauHouse in your future/past.
Also hardware store bolts generally suck, beware.
In America it’s standard to have a set of all diameter nuts and bolts attached to a shelf for the customer to test fit the one they brought with them.
I live on the planet Earth, so yes, I have been unable to avoid making this observation.
For almost all mainstream, especially consumer-market focused, low-grade fasteners, there is one common (coarse) thread pitch that is overwhelmingly common/dominant. If you see a 3/8″ bolt in the 5/16″ bin at the Homeless Depot, you can assume safely that it is going to be one with 16 TPI.
The only place where most people will ever encounter less-than-bog-standard thread pitch fasteners, is in automotive applications, all of which are standardized by the SAE. If you removed the flywheel or harmonic balancer from your 8.9 liter diesel engine, and you rounded off one grade-12.9 fine-threaded bolt, you’d better not be shopping for a replacement from the Orange Box Behemoth or the European Red and White equivalent.
I bumped into it quite by accident: I bought a piece of American kit which took 10-32 mounting screws. It took me about 3 goes to buy the right ones . It was labelled as 10/32 so I thought initially it was 5/16″. It also never occurred to me it would be a fine thread, because coarse M threads are roughly comparable to UNF, so metric fine threads are somewhat rare.
Anyway I was just making light of the imperial/US system where the conversion factors work until you get to screws under some critical size (1/4″??) at which point you get a not- quite-random number size.
At least that was my impression from buying a very very small selection of screws.
Reminds me of the approximate conversion tables in the first edition of Gamma World (the assumption being that the switch to Metric would be successful before any apocalyptic futures played out).
Although, then as now, there were many people too pedantic to see an estimate without having a panic attack. (“A meter is approximately a yard?! Egads!”)
As an American, I have a good feel for kilograms because of filament spools, and centimeters because a factor of 2.5 is not that difficult. On the other hand, my mental estimate for kilometers is about the same as my mental estimate for miles, which is to say, terrible
It’s ~5/8ths. Half it and add 10% of the original is a good estimate, within 5%. Even just “cut it in half” is only 20% off, which isn’t the end of the world.
100 kph/2 = 50 add 10% of the original = 60 mi/h, actual is ~62.5-ish. 300 kilometers = 150 + 30 = 180 miles.
Going the other way is actually easier (add half, you’re within 10%: add half and 10% of the original and you’re within 1%). 70 mph = 105 kph (not bad) -> add 10% of 70 -> 112 kph (within 1).
As an American who grew up in the ’70’s, I learned everything I needed to know from cartoons:
U.S. Office Of Education – “Metric Education” (PSA, 1978)
https://www.youtube.com/watch?v=JUXutV6Vk6k
As an european, I just sit back and enjoy the show…
It’s the same here in Australia :)
Summer weather where?
Note that most of Europe is north of the US, to the point that New York is basically at the same latitude as northern Spain, which is hot as far as Germany is concerned, and downright scorching if you ask a Swede. For a person born in a “metric speaking” country, you could just as well naturally know that 25 °C is summer-weather hot, and 35 °C is a national panic level heat wave reached once in a decade because nobody has air conditioners in their homes.
That’s another reason why people in the US have a hard time grasping what temperatures in Celsius mean: the US folk are used to temperatures that are common around South Europe and North Africa, while the metric and English speaking countries are situated much further north, except for Australia which is more like Mexico in terms of latitude.
For another point, when you have a hot summer day up in Sweden and the temperature goes to 25 °C, the sun is not high above your head – it’s lower in the sky, shining sideways at you and exposing your body to the radiant heat, making lower ambient temperatures feel much hotter when you’re out in the open.
When someone from the UK says 25 °C or 77 F is “hot”, it just doesn’t make sense to someone from Florida. Even if both were speaking metric, they wouldn’t agree on what is hot and what is cold.
35C is a common temperature here in Texas during the summer and, I hear, this week in Central Europe.
During a Texas heatwave, 95 F is at 9 AM.
Plus the lovely humidity.
Nope.
I’ll just keep dealing w ‘hippies everywhere’.
35°C in Central Europe can be easily simulated with magnifying glass and an anthill. As you would clearly see if you did the experiment yourself, all the Europeans rush towards the closest chunk of stone in sight and hide under them. Vast tunnels in some Central European cities are especially appreciated as are historical buildings.
Some Europeans, especially from the countryside, have a different strategy. They hide under lush vegetation watered using rain accumulated inside heavy barrels. This is an adaptation to a regulation that allows cities to charge fees for water going from roof directly into the municipal drain. Keeping the water inside barrels and letting it seep into the ground over extended periods is free. And Central Europeans love free. Most then proceed to invest saved money into either cold beer or wine to re-hydrate themselves during such extreme temperatures.
I’m a Floridian and I approve this message. In fact, I saw a short this morning from an Irish youtuber who was complaining about the heat at 28 C (which fortunately he provided the conversion as “82 foreignheit”) and I legitimately couldn’t tell if it was suppose to be satire or not. Today’s forecast temperature where I live has a high of 95 F (35 C) and a low of 76 F (24.4 C) with an 86% humidity. I don’t expect our highs to get down to the 82 F (28 C) range until late October/early November which is when we start considering that it is starting to cool off.
It takes two weeks for 28 C to start feeling “normal” to someone who’s used to having daily average temperatures below 20 C. If it only ever goes that high for two week in a year, it’s always going to feel brain-melting hot.
Don’t agree. It’s mostly airflow and humidity.
If you’re in an area that only gets in the 90s for a week or two a year, it’s because the wind died down, the area’s baking, and the humidity is probably rapidly rising. Those conditions would feel like hell anywhere.
In Hawaii, low-90s won’t bother anyone so long as the trades are blowing. If the trades die down it rapidly becomes miserable.
95 F with 86% humidity is 91 degrees wet-bulb. That’s rapidly approaching the limits of human survivability. This isn’t an “oh I’m used to it” thing. Your body cannot adapt to being unable to shed heat.
In my experience, 30C at 50-60% relative humidity in the beginning of the summer, regardless of wind, feels like my brain is melting. Couple weeks later I can get some sleep again and things normalize, and by the end of the summer it feels perfectly comfortable.
we have 40°C in summer, too, but due to taxes and tariffs we only ever see 25°C outside…
” the US folk are used to temperatures that are common around South Europe and North Africa,”
Uh, latitude does not equal temperature. You are woefully misinformed. Jet stream. Tell us about the European and North African blizzards in Spain and so forth.
It does not determine temperature, but it’s a very good predictor of what sort of climate to expect.
The warmer temperatures up north due to the gulf stream are actually an aberration, and the polar vortex breaking down and pushing snow down to Texas is likewise an anomaly. The US is more or less the temperature it should be according to latitude, while northern Europe is somewhat warmer than it should be; the overall trend remains.
Regarding snow in Spain – yes, it snows in Spain and even in Portugal.
Was part of “blizzard” somehow unclear? If so I owe you an apology.
Look up Storm Filomena. In 2021 Madrid got over half a meter of snow.
https://www.youtube.com/watch?v=-1krCFL1j9I
https://www.moroccoworldnews.com/2025/03/181649/morocco-braces-for-intense-snow-storms-and-gusty-winds/
Snow in Morocco is pretty much analogous to snow in Texas.
As an european, I do not just sit back. I warm my hot tub to 40°C before I get in, set the sauna for 80°C before I enter and I enjoy all 0.5 liter of my 5°C beer in the 20°C living room. Only then I am thoroughly relaxed. :-)
Someone is report-bombing this comment section.
I missed it, but it looks like we got it back under control.
“Do you have a favorite fast conversion back or forth from metric? Share it in the comments.”
That was tried and they were deleted en masse. If you don’t share them the author can’t delete them en masse as appears to have happened.
Okay. Canada is supposed to be metric.
So water freezes at 0°C and boils at 100°C. That’s your benchmark. 33°C is 1/3 of the way to boiling.
Your refrigerator is at like +5°C. -40°C is the same -40°F. The temperature here gets to that point. Don’t go outside. The air will try to kill you. We like it that way. Lets you know you’re alive. If you’re careful.
And distance isn’t measured in km. Its measured in hours.
“How far is it to that town/city/place?” “About 2.5 hours drive” or like “20 min walk”
Weight of food is in kg. Nobody really gets it unless they work at a butcher shop.
Weight of people is in lbs. Even though your driver’s licence will say it in kg.
The big bottles of pop (soft drink) are 2 L. Milk is half that size or the same size if you’re thirsty.
The weather is terrible. Its either too hot, too cold, or too wet. All you really need to know is:
1) Wear sunscreen, a hat and a shirt. +30°C may not feel warm to some people but heat stroke is real.
2) Do you need a coat or not?
3) When in doubt, layers
4) Parkas are for -20°C or colder. Otherwise you’re not doing #3 properly.
10 feet are 3 meter so
meter to feet is m / 3 x 10
feet to meter is feet / 10 x 3
Note 3 feet or a yard is not exactly 1 m but quite close
So you consider an 8.5% error “quite close”. You go ahead, I’ll catch the next one. Safer that way.
The simpler and much less inaccurate approach using the same digits is to look at a ruler and note that there are 30 centimeters per 1 foot. Go with Christ, brah.
i love that soda comes in 2 liter bottles instead of half gallons, and whiskey comes in a fifth gallon instead of 750mL.
Re the 2 liter bottles, seems that decades ago the U.S. had a big push to go metric. It was probably expensive to modify or even replace bottling machines; few people seem to mind liters.
“…The weather is terrible. Its either too hot, too cold, or too wet. All you really need to know is…”
“…When I was growing up, we were too poor to afford any way to check on the weather, so we had a ‘weather dog’—a black dog.
Here’s how that worked:
You opened the front door and threw the dog outside.
If he came back thirsty, it was hot.
If he came back wet, it was raining.
If he came back white, it was snowing.
If he didn’t come back at all, it was really windy.”
—anon
The cool thing about miles and km is that they approximate a Fibonacci sequence. 2 miles is 3 km, 3 miles is 2+3=5 km, 5 miles is 3+5=8 km, 8 miles is 5+8=13 km, 13 miles is 8+13=21 km, etc
i feel like a dork for estimating inches to (milli-, centi-) meters by matching the firearm calibers that I know in both… it works fairly well.
I recommend this approach to metric temperatures: 10 C is cool, 20 C is pleasant, 30 C is warm. (You might need to shift this up or down by 5 C or so depending on your personal tolerances, but that seems to work well for many people.) Numbers in between are in between. :-) For bonus points, 0 C is freezing … and 100 C is dead. ;-)
For km to and from miles, I have a couple of nerdy tricks that work well for us nerdy types, though I wouldn’t recommend them outside of that circle — but they’re cool and y’all will get it, so here you are. For the first one, observe that the ratio of km to miles is roughly 1.6 to 1 … which means it’s the same ratio as hexadecimal to decimal. When you see a 25 MPH sign, you can convert 25 decimal to hex and get 37 km/h, then just round up to 40 km/h — and that’s just about bang on.
The other way to do it is to observe that the ratio of adjacent Fibonacci numbers is also around 1.6 to 1 (really 1.618… to 1, the golden ratio, but whatever). So just as 5 is adjacent to 8 in the Fibonacci sequence, so is 50 MPH about equal to 80 km/h.
Both of these tricks also work in reverse, obviously. Happy converting!
“10 C is cool, 20 C is pleasant, 30 C is warm.”
I had a teacher that taught us that as a short rhyme: “30 is hot, 20 is nice, 10 is cool, 0 is ice”. 86°F, 68°F, 50°F, and of course 32°F, respectively. Very ballpark but easy to remember, and it can be surprisingly accurate to estimate between those steps without having to get out the calculator. “Brrr, the heat is out, it’s only 14 C in my apartment”, so a little less than halfway between 50 and 68, so it’s like 57 or 58ish? Yep, 57.2°F. Closer than the precision of a cheap thermometer anyway. Bonus points if you can remember to add 40°C=104°F for summer heat waves.
77=25 is just about all I ever needed, plus this rhyme.
Hexadecimal. Awesome.
Careful with speeds above two digits mph, or you will relive your (Grand Prix of) Montreal experience
US was among the first to push for metric system more than a century ago and it was required in my elementary school in the 70s. Unfortunately it died because the cost of replacing bazillion road signs (miles marker, speed limit, etc) would mean everyone in the congress would have to take a big pay cut for a few years.
Military, NASA, and some industrial and commercial does use metric but the average American wouldn’t know if 40°C is too hot or not.
PS I lost 35kg in the past few years. Doesn’t seem like much when you compare to 77 lbs I lost in the same time
My first winter in Munich was cold in the mornings when we were out walking the dog. Never translated the units, but I got the feeling that -10 °C is pretty cold, but with appropriate clothing, possible.
At some point, I was talking about this with my folks, converted it into Farenheit. What the hell was I doing outdoors when it was 15?!?1
For word nerds that want to know where all these unit, imperial and metric, names come from. Check out Robwords video at:
https://youtu.be/pM3c328VifA?si=aaKiPBuSqLuhfgDr
Good vid. He goes with 2x celsius + 29, splitting the difference on Al’s two methods.
For the PCB people who think a thou(sandth) or an inch is the same as a milii(metre), please just stop trying to be technical.
And for the people who can’t spell metre (e after r) please also stop. Just because you branched a language into a new language doesn’t mean the correct spellings go away.
That’s exactly what ‘branching a language’ means limey.
Not just spellings.
For example:
In England it’s pronounced ‘Frounce’.
In America it’s pronounced ‘FrAnce’.
We know the French don’t like it, why we do it.
in the year 3535,
people will still be “upset” and feel “correct” about the spellings of words in different cultures.
Times change, science changes, immaturity does not.
“…The metric system did not really catch on in the States, unless you count the increasing popularity of the nine-millimeter bullet.”
—Dave Barry
Funny how we in the US are stuck with the British Imperial System, yet Britain no longer uses it. Now that the Brexit is over, can we just export it back :-?
Unrelated, one of the major flops was with failing to switch to the 364 calendar year. Not metric or imperial, but COMMON SENSE.
364 / 7 = 52 workweeks, and there were variants as to how many days are in each month; the initiative that flopped proposed 13 months, each having 28 days; there were other alternatives – four quarters/seasons, each having 91 day, which would make two months with 30 days followed by the month with 31 day (91 / 7 = 13, so while weekdays would be changing inside each quarter, quarters themselves would start and end on the same weekdays regardless). Remaining 1 or 2 (leap year) days were to be set aside as a permanent end-of-year holiday/holidays.
Having said that, seeing how long it took to establish UTC (global Universal Time), changing to the 364 calendar may take few centuries, give or take three hundred years. By that time the Earth may even slow down enough to add another full day worth of hours, so it will probably make more sense to just get it over with and introduce a 5-day workweeks, because 365 / 5 = 73. (SARCASM! SARCASM! SARCASM!) I’ll leave it as an exercise for the reader to come up with some kind of meaningful (and entertaining) breakdown for 73, because it is a prime number :-]
Sorry about the run-on, but there are multiple rabbit holes leading to (or forking off) the metric-vs-imperial hairsplitting herewith. One such hole has to do with the number representation/representations that were designed to ease the everyday calculations; romans had their idea with the digits, ie, hand fingers, hence, I, II, III, V, etc. – you do the math curling/uncurling fingers; Mayans had bars and dots and 12-base math that remains me of the abacus of a sorts; I’ve also heard of 13-base math and 20-base math, though, not sure how one would represent or calculate with these.
The value of 1.8 always seemed much easier to me.
USian. Born here. Live here. Think in SI. All of the BS in the 1970’s (100 years after the US officially adopted it and rejected Imperial) was mostly BS. More accurate? no. Faster? depends. Easier? yes. Because it is unambiguous and consistent.
Over the last few years, I have had issues in my professional life with the BS units over: Barrels (three different ones, IIRC), ounces, gallons (three or four different ones, at least), tons (three), degrees (two, but multiple times), and pounds vs Kg (I have no f’ing clue how that happened). Oh, and hundredweight. (100lbs US vs 100lbs UK, vs 8 stone whereevertheflock)
The worst, and most expensive, was the gallons issue. It wasn’t between the various kinds of gallon, it was a gallon container that was actually two litres. NOTHING in the literature from the supplier said anything other than gallon. We figured a gallon at a bit less than 240 cubic inches. at roughly $US400 per ‘gallon’. Fortunately, we preplanned the next job and had sufficient material, but ate maybe $30K one the job. There was a LOT of material used.
I’ll deal with 220417.5mm all day long to not have to deal with some of the messes I have had to deal with.
“I’ll deal with 220417.5mm all day long to not have to deal with some of the messes I have had to deal with”
That’s easier than ~220.4 meters? Okay you do you. When increased accuracy is needed it can be applied but the meter is the standard unit, not the M&M.
Metres vs mm depends on the industry. Some use both. One side of my engineering life, EVERYTHING is mm, with the largest scale being about 350m (350000mm), the smallest being 0.1mm in the side I work, though many components are at the mm to 0.001mm scale.
Not me doing me. Common in the industry.
I mean in the system, not in industry. The name fits.
“The worst, and most expensive, was the gallons issue. It wasn’t between the various kinds of gallon, it was a gallon container that was actually two litres. NOTHING in the literature from the supplier said anything other than gallon.”
This is totes adorbs! A liter is just over a quart so two liters is just over half a gallon. You couldn’t eyeball that the containers were half the size they should be? Or did you just eat the weights and measures fraud? US born, US live there, have you ever seen a dairy display in a grocery store? The name fits.
Maybe they didn’t see the container that the supplier was calling “a gallon” until they received the shipment and found out it was actually half a gallon, and the entire shipment was half the material they though they had ordered.
“Or did you just eat the weights and measures fraud?” Dude, I can read, can you?
IAP: You ever deal with the real world? A large job in the real world? nomen tum mihi omnia quae scire debeo de te indicat
Maybe a large job in the real world where the stakeholders are from three continents, and the materials come from suppliers/manufacturers on all three? Directly to the job, the day it is starting?
This kind of mistake happens. You build it into the bid. Sometimes you win, sometimes you lose. The stakeholders know this, and, since it costs a lot more to deal with messed up job (like, for example, another contractor not mixing the catalyst, but just pouring it into the void on top of the several hundred Kg of resin, requiring several days to clean the mess, an environmental flag, a rush fabrication of replacement damming/fixturing, rush shipping of more material, additional time for other crews and contractors who are now sitting on their thumbs, penalty charges, demurrage, and so on) know that this is built into every bid for non-routine work. They also know that the bid will be tight on the next five of the same job.
After that, I think our purchasing agent made the supplier cry. It was made abundantly clear that they should know the basic details about their product, not just what is on the outside of the carton. I only heard his side of the call, but I would’ve cried.
“You couldn’t eyeball that the containers were half the size they should be?”
Funny thing. The containers were actually larger than a one gallon paint can, maybe five quart or 1-1/2 gallon size, and the same style. High density resin, so the mass was no indication. Oversize can is expected, as the mix is done in the can with a stir head in a drill. If the can isn’t oversize, you lose product over the edge.
Opened the first can on the job, saw it looked way short, first thought was that looks like a lot more extra space than is needed for mixing. Looked at the stock we brought, figured we were good, and did what we had to. Had to order more material for the next job.
I routinely curse the ghost of Ronald Reagan for cancelling metrication. I was promised we would go metric, taught it in grade school, and then his political advisors told him it would be bad politically. It’s not the most evil thing he did but was certainly annoying and is a big tech debt on American industry.
I have my own peculiar way to convert miles to km and vice versa. It might only work for me as well!
I am using a Fibonacci sequence such as
1 1 2 3 5 8 13 21 35
And 1 mile is 1.609 km so roughly 1.6 which happens to be very close to the golden number. Why does it matter, because Fibonacci numbers are a power of the golden number.
Let’s say you want to convert 50mi to km then pick the following number in the sequence (yes, I multiply all terms by 10) so 50m is 80km or 130km is 80mi pick the number to the left to convert miles to km
I found it pretty efficient to convert my speed limit on the road but that may only works for me!
I often do rough estimates from correct units to freedom units, I use these quick and easy (rough) conversions:
– 1dm is 4 inches
– 10sqft is just under 1m^2
– km+km/2(+km/10) is miles
– kg/2 is lbs
lbs/2 is kg … sorry, that has been working on my nerves
A few other nice to remembers, that are generally good enough:
Cooking temperatures: F = 2C (150°C = 302°F, 200°C = 392°F, 250°C = 482F)
Distance:
3 ft = 1 m (0.91)
10 ft = 3 m (3.05)
1 mile = 1.5 km (1.61)
3 miles = 5 km (4.83)
5 miles = 8 km (8.05)
Volume:
4 cups = 1 liter (.95)
1 washing machine = 3 metric microwaves
“3 ft = 1 m (0.91)”
That’s an annoying error. Just small enough to seem insignificant, but big enough that you end up counting wrong by tens of meters when you’re pacing distances, and hundreds of meters wrong when trying to navigate and orient by map. You see, the average human stride is closer to a yard than a meter.
Many years ago, when we had copper wires for our rotary phones, and the primary mass communication was via EM waves in free space and low-grade dead trees, I attended a uni near the Canadian border. Like many, it had a radio station with student DJ’s playing various types of music, mostly children’s music at that time (by the Tom Lehrer definition), and had students also presenting things like the weather and news.
The morning weather report one cold day was the last for the presenter. I don’t recall the actual temperature, but think mid-february on the upper peninsula during a cold year. The report went something like “Today’s high will be about -10 degrees. For you on the Canadian side of the border, that’s -24 centigrade. If you are at the engineering college, that’s 250 Kelvin. If you grew up here, It’s gonna be cold. Wear a coat”
Another way is to just use metric and don’t think so much of F. The fact 0 C is freezing and 100 C is boiling, and 25% along they way (25 C) is room temp. What else do you need? +-5% is comfortable without a jacket (that would be 25% +- 5% aka. 20c to 30c). Under 0% you have to worry about water ruining your day one way or another due to freezing. Around 0% (say +-5%) you also have to worry that it may freeze, thaw, or be cold as hell as some moisture in the air has still not dried up. At 100% you have to worry about that water exploding in your face due to boiling.
People in the colder regions don’t start to wear jackets outdoors until the temperatures drop below 18 C. “Room temperature” is likewise about 18-22 C.
https://en.wikipedia.org/wiki/Thermal_comfort#Adaptive_comfort_model
So the idea that 25 C is “room temperature” is not universally agreed.
As mentioned earlier for temperature conversion, the math trick of subtracting (or adding) 10% to double the C number will be as accurate as to how many decimal places you can carry in your head. For example:
17C x 2 = 34, 34 – 3.4 (round this up or down and you will be within a degree) = 30.6, 30.6 + 32 = 62.6F
Conversely 84F – 32 = 52, 52 / 2 = 26, 26 + (2.6 + 0.26 {2.8}) = 28.8C. From F to C it is necessary to add 10% of the 10% to get closer to the formula conversion.
Well fahrenheit is the more precise scale
As one degree of changes in Celsius is multiple degrees in fahrenheit
But take farhenheit subtract 32 gets you in the range of Celsius
100F is about 30 Celsius
32f Freezing is 0
And 212f boiling water is 100
And zero farhenheit is like -20 or something
It’s only 30 degrees
Shit sound like it freezing to me
Oh you’re not using fahrenheit 🤷♂️
Uhm, we use subdivision with Celsius you know, when I check the weather it’s 26.3℃
And I just checked and the US weather uses whole numbers it seems. Odd, but it explains your confusion.
(repost to get it in the response to the right person. Thanks HAD comment system)
98.6 degrees says you’re completely wrong. A third of a degree C is close enough to a half degree F as to make no difference and “blah blah and a half degrees” is not unheard of in the U.S. The assertion was the F is a finer scale than C and it is and you are wrong.
I’m only ‘wrong’ in your troubled mind.
Celsius is ALWAYS defined in float (not just with the weather BTW), and the SI unit is Kelvin not Fahrenheit.
(Fahrenheit incidentally was a guy born in the Polish–Lithuanian Commonwealth and from German origins, so don’t try to make it a USA USA USA thing).
As for the numbers used in the US: to check I went to weather.com and looked at the map there, it had whole numbers. No idea of the frequency of the use of fractions but I don’t recall hearing or seeing those a used a lot with Fahrenheit, or in fact ever, which would make sense if the scale is finer when using whole numbers.
But the scale in whole numbers is not relevant if fractions are the standard with Celsius, you still have the same precision obviously. You can use fractions with both and go so far that the numbers becomes meaningless due to the limitations of the physical world and there is no difference in precision, unless of course you have some kind of mental issue that makes it impossible for you to use fractions. In that case I happily support you using Fahrenheit all day and night in the comfort of your mental institution.
“I don’t recall” is hardly evidence. The machine displaying vital signs in my hospital room proves you wrong. 98.6 (37C) wasn’t a clue?
A small correction in the interest of being honest: When cooking instructions give a temperature it’s whole numbers in Celsius, because ovens are not precise enough nor consistent across brands to use any precision. anyway.
“But take farhenheit subtract 32 gets you in the range of Celsius”
That’s a hard F*** NO! Redo, resubmit.
For converting inch fractions to mm in my head, I use the binary inch: 25.6 mm. 0.8% error, good enough for most uses.
“For converting inch fractions to mm in my head, I use the binary inch: 25.6 mm. 0.8% error, good enough for most uses.”
So you prefer a guaranteed error to using the correct value of 25.4? I will never understand you people.
For mental arithmetic, yes. I’m not going to whip out a calculator to figure out how much 5/32 inches is. Whereas 256/32 is 8 so it’s 5 = 0.8 or 4 mm.
The actual value is 3.96875 mm, so I’d need to fish out the Mitutoyo to be able to measure that kind of difference.
3 feet to the meter makes a good estimate, but 100mm is 4 inches with an error of 1.6mm. A square meter is 10 sq ft, or close enough for comparing houses and rooms and carpets and property
When it comes to human interface, note that scale settings on instruments usually got in a set pattern 1-2-5-10-20-50-100-200-500-1000 because powers of 10 have far to large a gap.
The 9/5 approximation was used because it’s simple to do in your head. Multiplying by 9 and dividing by 5 are both easy.
For C to F the process is pretty straight-forward:
9X = 10X – X ; for example: 23 * 9 = 230 – 23 = 207
X/5 = X/10 * 2 ; for example 207 / 5 = 20.70 * 2 = 41.40
and finally add 32 back to it. and you have 73.4 F = 23 C
That said, I think it is more important to have an intuitive understanding of different units. Like draw some 1 cm, 5 cm, and 10 cm lines on a piece of paper and compare it to different items in your home. Fill some of your glasses with 0.1 L and 0.2 L and 0.5 L to see what that volume looks like in some typical containers.
And of course I like to fill a bucket with salted ice water slurry and another bucket with fresh horse blood and dip my hands in each to get a sense of Fahrenheit’s original 0-100 scale. There’s no need to do this for Celsius because it’s already intuitive, you know what ice and boiling water feel like.
This video instantly come to my mind:
https://www.youtube.com/watch?v=JYqfVE-fykk
The temperature part of this is useful.
But the problem with intuition is assuming that someone else has it…
Over the last 20+ years I have ,ade it a habit to stop random passersby and ask them how far something in the distance is. I picked miles/km based on what the locals used.
When I was in northern Italy I picked a visible mountain.
When living near an inlet I picked a lighthouse on the other side of the bay.
When living near a city I usually picked a tall building.
My question was usually: Do you think [thing] is 2, 10, or 20 [units] away from here?
Almost everyone gets it wrong.
Like…maybe a 3% success rate.
I have asked hundreds of people this question over the decades. Maybe more than a thousand at this point.
I have asked it in at least 8 countries across 5 continents.
When I get a rare correct response the person always turns out to work a job that actually requires, or at least constantly uses these units like a surveyor or a pilot.
People just have NO intuition for distances if they don’t work in a job that uses them constantly.
For a few years where I lived in places that were too flat to have something distant, I used much shorter things between 10-20 feet/meters tall.
I got more correct answers, but still no more than 10-15%.
In the US where I live, I also sometimes ask people if a mile is about 1000, 5000, or 10000 feet.
Most people get this wrong too.
I just have no idea how ‘normal’ people can operate in the physical world without having these basic intuitions.
A gallon of water is about 8 pounds.
A kg of water is a litter.
Shunting (railway) gives you a good estimate on distances, but commonly in “Längen” (1 Länge is 10 m according to the rules, but in real life it is whatever the length of the cars nearby is, usually between 9 and 27 m. Only important thing is not to vary the length during the shunting operation). The big advantage is, you don’t have to guess, but you just count whatever appears periodically alongside the track. For the last bit one usually changes back to metres, because they are shorter.
Typical radio transmission during approach: “10 Längen” … “8 Längen” (now the distance for 1 Länge is defined for this approach) … “6” … “vier” … “drrrei” … “zwo Längen” … “eiiine Länge” … “halbe Länge — drrrei Meter, zwo, eiiin Meter, Penislänge, uuund halten.” (or “zwo, eiiin Meter, halber Meter bei” if you want to stop transmitting early, for example if you have to catch a car without brakes applied, so you have both hands free on impact — don’t do this if someone is watching, but sometimes you just have no choice)
By far the worst freedom unit is the acre. The amount of times I have had to grab my calculator to divide by 43560 is absolutely mind boggling. I bet our surveyors and civil engineers would gain at least a few percentage points more productivity if we got rid of the acre. On top of its dumb definition, I bet very few people have any sense for what an acre looks like. Let’s make new freedom units. Myriafeet, and square Myriafeet. The old SI prefix for 10k.
Typical politician got elected by promising ‘Every man will have two acres.’
When he got elected, he kicked all his male constituents in the balls.
Europe still uses the hectare, which is no better.
IIRC 1 hectare = 2.5 acres.
Both based on furlongs or some such.
An acre is 2 of my CA house lots, or between 7 and 100 SF bay area ones, not hard to visualize.
Also and acre is about 0.75 of a a football field, about the same for soccer.
1 hectare = 10 000 m^2 (1 are = 10 m x 10 m)
https://en.wikipedia.org/wiki/Are_(unit)?useskin=vector
One redefined ‘metric hectare’.
It is an old unit.
hectare comes from the Greek root hekaton ‘hundred’ + are
“In 1795, when the metric system was introduced, the are was defined as 100 square metres, or one square decametre, and the hectare (“hecto-” + “are”) was thus 100 ares or 1/100 km2 (10000 square metres).”
“The metric system of measurement was first given a legal basis in 1795 by the French Revolutionary government. The law of 18 Germinal, Year III (7 April 1795) defined five units of measure:
The metre for length
The are (100 m2) for area [of land]
The stère (1 m3) for volume of stacked firewood
The litre (1 dm3) for volumes of liquid
The gram for mass
“
Regarding the quick, approximate (i.e., SWAG) conversion from °C to °F —
it’s been said before, but the absolute simplicity and utility of the “2X+30” trick (…was going to say ‘algorithm’, but that would make it a certain turn-off for some) needs repeating…and remembering. (“2X+30” means “Multiply the Celsius temp by 2; then add 30 to get the approximate Fahrenheit temperature”).
As one who traveled a lot to really diverse geographical locations, I had to continually check on the destination’s weather in order to pack and dress for comfort. The “2X+30” rule was invaluable.
Here are some examples from today, for your consideration:
(RT = ‘real temperature’; SWAG = ‘2X+30 temperature’)…
It’s 29°C in Hong Kong right now…
SWAG temp: (29 x 2) + 30 = 88°F
RT = (29 X 1.8) + 32 = 84.2°F
It’s 23°C in Tokyo today…
SWAG: (23 x 2) + 30 = 76°F
RT = 73.4° F
In Antarctica, somewhere, it’s -48°C…
SWAG temp: -48 x 2 = -96 +30= -66°F
RT: -48 x 1.8 + 32 = -54.4 °F
These SWAG esstimates are close enough for most needs, most times…
I don’t worry to much about it. We all have 2.54 on the brain from high school, as well as 3.14159, 2.71828 and a few others on tucked away. We go to the store and buy a gallon of milk or pound of butter. But I design my FreeCad projects in mm. Oil plug requires a 14mm socket… So it goes. All one half dozen of the other….
As a Canadian who happens to live in SW Ontario, near the USA border, I have been doing this my entire life. In fact, our radio broadcasts give the weather in both Celsius and Fahrenheit. Our meat is listen per pound in the sales ad but actually sold in kilograms. You kind of just get used to working with both systems.
The best way to learn is to just switch. Don’t try to do the conversions. I’ve lived in the US all my life, last year I switched all my devices from F to C. I can tell you that It’s 21C outside right now and it’s an enjoyable temperature to have my windows open. Later today it’s supposed to get up to 27C and I’ll have to close my windows and turn on the AC. I cannot tell you what those temperatures convert to in F off the top of my head. I don’t care and it doesn’t matter. I’ve internalized how those measurements feel to me.
Honestly, I somewhat agree except for the fact that I still have to deal with my local news, my family, etc. who have not converted. It is kind of like the dvorak keyboard. I always think I will use it. Switch over. Like it. Then get killed when I have to use someone elses’ computer and switch back… So I’m with you. I’m (whatever bilingual is for metric measurements) but until I move or everyone is, I think you still have to do the math or at least approximate it. Plus, if you want to get there, the rule of thumbs help a lot in my experience.
That’s a preference. Like above everyone I interface with uses degrees F. So that is what I use. On the other hand, I set my computers up to use 24 clock as well as phone and watch. My personal preference. Now if we can just get rid of Daylight Saving Time…. More important than what ‘units’ we use.
One can’t reply the most nested comment because the “Reply” is not showing for level 6+
Tested with chrome, firefox and edge
I use the 3m=10ft and 30cm=1ft approximations in my head. Also, 5m=16ft.
Fractional inches drive me nuts. I’d much rather use mm — it’s close enough for household carpentry.
Nobody’s yet brought up shoe sizes, which in US/UK are in barleycorn unit increments (from one integral size to the next is 1/3 inch difference). At least the Brits size men’s and women’s shoes the same; here in West Pondia a women’s 10 is a men’s 9.
I still remember the imperial to metric conversions that were printed on the back of cereal packets in the 70s when the UK switched over.
A meter measures 3 foot 3 (inches), it’s longer than a yard, you see.
A liter of water is a pint and three quarters.
Two and a quarter pounds of jam weigh about a kilogram.
I’m fortunate that the currency changed before I needed to worry about that, there used to be
4 farthings in a penny
2 halfpennies in a penny
3 pennies in a thrupenny bit
6 pennies in sixpence,
2 sixpence in a shilling,
10 shillings in a half bob
20 shillings in a pounds
21 shillings in a guinea
There were a few others as well ;)