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!


  1. Brian Wall says:

    just learn this in school today

  2. Exit151 says:

    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..

  3. Boracho says:

    this is kinda nifty….I don’t have a lamination machine though….PACKING TAPE TO THE RESCUE!

  4. Spike Martinez says:

    Bad boys rape our young girls but Violet gives willingly. Anybody?

  5. Will Lyon says:

    I use Electronics toolkit and Adafruit’s app on my ipod touch

  6. svofski says:

    I use an ohmmeter. Can’t be bothered decoding this nonsense.

  7. andarb says:

    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. :)

  8. Smonson says:

    I suggest adding silver and gold to the next version (for 0.1 and 0.01 multipliers), those are the ones I can never remember, and need to look up!

  9. KnightFire says:

    Canadian Old School:

    7 = Violet
    8 = Grey

    0 1 2 3 4 5 6 7 8 9
    Bad Boys *ape Our Young Girls But Violet Gives Willingly

    Learned it once 30+ years ago, never forgot.

  10. Miff says:

    I memorized the color code because of XKCD:

    “Be Bold, Respect Others, You’ll Gradually Become Versatile, Great Wikipedians!”

  11. Deg says:

    Thank you for saying, “I”, rather than “we”. There actually is a human writing articles! No awkward grammar and sounding like a borg collective…

  12. Bubba Gump says:

    Bad Boys Rape Our Young Girls But Violet Gives Willingly? Who is doing the raping? ELI the ICE man? LOL…

  13. Scott says:

    “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”

  14. Justin Case says:

    but veronica goes willingly (for) silver (and) gold

    isn’t no band 20%?

  15. Whatnot says:

    So, not a single picture in the comments but stupid mnemonics instead, sigh.

  16. Frank Buss says:

    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.

  17. sanjay says:

    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

  18. Trui says:

    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.

  19. A Bryant says:

    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)

  20. rue_mohr says:

    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?

  21. static says:

    I have slways thought resisto rcolor had aid worthy of reproducing


  22. 3gfisch says:

    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

    • Sebi says:

      “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 ;)

      • Nitish says:

        “In ancient Rome”, not “in the ancient rome” — im (= in dem) alten Rom ist Deutsch !
        “Lands” does exist, you can say “In foreign lands” in English.

  23. The “Ohms Law Circle” would be better to have than the single I=V/R

    If you don know the the resistor color codes by heart you probably can’t transpose the U,R,I,W in a formula in your head either…

  24. Sven says:

    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.

  25. w says:

    Hurrah for desktop publishing and bandwagon jumping :D

  26. Jared says:

    nice, sometimes keeping things simple proves to be the best way. That said the EEVBlog ruler is awesome – just because Dave made it. I’ve ordered some :P

  27. ka1axy says:

    Ohm’s Law has always been: E=IR to me…E is for Electromotive Force (what Voltage calls itself on official forms)

    …and +1 for “Bad Boys…”

  28. SuppaUppa says:

    Please excuse my rudeness but I cannot stand authors using “I” in their posts. This isnt your blog.

  29. What's in a name? says:

    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…

  30. Phrewfuf says:

    Nice Ohm’s Law you have there…would be a shame if the big V would stand for Volume not for Voltage.

  31. Edware says:

    How about an iPhone/Android app where you take a picture of the resistor(s) and the phone decodes the bands, those that are usable, and prints the value.

  32. If you took basic electricity class you should know that by heart!

  33. Miroslav says:

    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.

  34. ameyring says:

    My resistor chart looks similar but was found in the back of one of Forest Mims’ small electronics books back in the 1990s and it’s still on the wall of my workshop.

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