Hackaday’s Resistor Code Reference Card

Check out the resistor color code reference cards I just whipped up. I was inspired by the PCB versions that Octopart has been crowdfunding this week. Those didn’t have the information I would normally be looking up, so I decided to whip up a few of my own and put them out there for inspiration or for you to print yourselves.


The story behind this is that we got several tips about the Octopart cards. Don’t get me wrong, It’s pretty cool to have a PCB refcard. But the information on the front is just the color code itself (three times). The back is a set of surface mount footprints. I don’t find those footprints useful unless its a way to test out custom outlines I designed myself. If I were to order something like this I’d lean more toward the µRuler which [Dave Jones] designed and recently did a small-run open order. I very nearly pulled the trigger on that one. Maybe next time.

resistor-refcard-backWhy let the information itself spoil the fun? I got to thinking about stuff I look up a lot. The resistor color code chart is always nice to have on hand, so I included that. Tolerance is one thing I just don’t have memorized (except for the gold 5% band, of course). I also like to look up some SI units to make sure I’m doing my math right. The four most common for me are included on the front just below the Ohm’s Law equation.

On the back is a cheat sheet for reading surface mount resistor codes. [Mathieu] already mentioned that codes with ‘R’ in them can sometimes include a multiplier. Oops! Next to that is a three digit capacitor code reminder which I almost always end up looking up. The power equation is one that I pretty much always know, but hey, there was space for it.

Make one of your own

I whipped this thing up in under an hour using The Gimp. Check out the XCF files, along with the PNG exports shown above (these actually have transparent backgrounds), and the PDF contact sheets I printed for the project. They’re up on our Github repo. I decided to try two different background colors. I’m a fan of the bisque shown above, but also ran half of them in white.

I went with my local Fedex Kinkos print shop. I was able to upload the PDF files in advance. They printed two double-sided copes (one of each color) for me. I feel that the $2.91 cost of this is a steal because it means I can get away with a super-cheap black and white laser printer at home. When I picked them up I also used their paper cutter to separate the cards from the sheets. After using the paper cutter’s grid table to align the cards I laminated twelve at once using an 8.5×11 laminating sheet. The finished cards were cut into singles using the same paper cutter. Lamination was $2.10, bringing the total project to $5.01 — that’s 42 cents per card which is a big break from the $9 the Octopart version is asking.

Of course if you want this on a PCB why not use spray adhesive to affix it to some copper clad, then top coat it with clear acrylic spray. Maybe that just sounds easy to me because I actually have all of those things on hand.

If you make your own reference cards we want to see them. Post them below (actual cards you’ve made… no mockups!). I recommend posting your picture to imgur and using HTML img tags in your comment. This should be fun!

76 thoughts on “Hackaday’s Resistor Code Reference Card

  1. Not to knock what you’ve done, but a REALLY great ‘tool’ is a program called “ElectroDroid” for Android devices. Has this and TONS more all in the palm of your hand and includes all sorts of useful charts, pinouts, etc..

          1. Maybe someone will take that too seriously, but if the boys are a certain color it sure helps you not mixing up the first two colors (it’s Black–>Brown, as opposed to Brown–>Black). This will become my new favourite!

  2. Can’t always trust the DMM when the existing part is in situ or defective. Not to mention that, while I strongly agree with Einstein’s comment about memorizing things you can look up, old-timers in charge of hiring will often quiz you on color codes because they expect every electronics tech to know it. If you don’t, tough luck try again.

    It’s not so hard, really. Black-brown-rainbow correspond to the numerals is the most important part. Even if you have to count on your fingers to be sure. :)

    1. If you think about it, the rhyme works better if you start with “Black” instead of “Bad”.
      Unfortunately it makes you feel like a terrible person every time you use it.

  3. “Clean” version: Better Be Right Or Your Great Big Venture Goes West
    And to add to the “Bad Boys” theme, Gold, Silver “None” tolerance bands, “Bad Boys Rape Our Young Girls But Violet Gives Willingly, Get Some Now”

  4. Nice, but mixing names and units for ohm’s law doesn’t make sense. You wrote I=V/R. “I” is the name for current, which is measured in ampere, “R” is the name for resistance, which is measured in ohm and “U” is the name for voltage, which is measured in volt. So the usual formula is I=U/R. Or if you want to use the units: A=V/Ohm.

          1. Yep. I learnt U is the name of Voltage in school in Germany. And I always thought V as name for Voltage would be an American thing. Like drawing resistors in schematics as zigzag lines.

  5. a bit late for this don’t you think ?

    I haven’t seen a thru hole resistor in a new electronic gadget for a few years now, 90% of my (hobbyist) boards are SMD and except for a few grey old guys whose eyesight is too poor to work with SMT, most of the people I know have moved or are moving to SMD

    1. +1 to that. The 1980’s are over. Anybody can solder 0805 with just a cheap but half decent pair of tweezers and a couple minutes of practice. There’s just no excuse anymore.

  6. I would recommend putting the color combinations of the E12 range on the card too. These are the most common combinations of colors, and it’s easier to memorize them with some context.

    But really, use SMD components. Anybody who can solder a through hole resistor can solder an 0805 SMD.

  7. Who is this Violet girl?
    Bad Boys Rape Only Young Girls Because Virgins Give Willingly!
    Big Bad Richard of York Gained (Gave depending on which part of the UK you come from) Battle in Vain

    As someone who has been doing electronics for 20 years, I have never heard of “U”

    However the more accurate Ohms law is

    I = Vs-Vl/R

    Vs = Volt Supply
    Vl = Volt Load (device to be powered)

  8. I learned via a training program I wrote, that just burns it into your mind by repeditive random questions, you dont think about it, you just know it. I lost the origional source, but wrote this later. you can try to cheat all you want with a reference beside you, but you cant play for 2 hours without knowing colours/numbers off the top of your head.


    I’m late on this post so I suspect nobody will reap its benifits?

  9. why Volts=V?? Unit symbol and the Dimension symbol should be two different things. so in germany and i thing most other lands Volts dimension symbol is = U
    so ohms law: U = R * I

    1. “Countries”, nicht “Lands” – Vielleicht hast du davon schon einmal gehört ;)

      Yep, that’s what I wanted to say: That awkward moment when you realize it’s “U” and not “V”. That would only be acceptable in the ancient rome ;)

  10. Why are the number codes in color while the tolerances have their colors written out in text?

    The usual way is to add the tolerance annotation to the side of the color chart.

    The uses of silver and gold for 0.1 and 0.01 multipliers is also missing.

    1. Is this sarcasm? When the author writes about a personal project it sounds pretty reasonable to use “I”. Besides, when they use “we” to describe their opinion on something I find it very unlikely that ALL authors actively discussed each opinion and came to an agreement on their shared opinion. IMO “we” is way worse.

  11. I’ve looked at so many color banded reistors over the years I just sort of remember what the color values are without fancy (or vulgar) sayings or cheatsheets. And I probably see more precision resistors with no color codes at all or SMD on a daily basis than with, but one glance at the ones with bands and I just automatically compute the value. Of course I don’t retain a bunch of useless movie quotes, song lyrics or video game cheat codes either…

  12. U is symbol for voltage not only in Germany, but in many countries of Europe as well. At least I speak for former Yugoslavia… I just checked wikipedia: German, French, Russian U, Spanish V.

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