Online resistor code tool

Online resistor code tool

Dave Fowler, of uC Hobby, sent us a link to this java app for determining resistor code values. There are a lot of these resistor ID tools floating around, in different formats — it’s nice to have the option to use which one works best for you and your circumstances (for instance, I don’t have a computer at my workbench, so it’s easiest for me to just use my DMM or one of those paper dial IDers I got from Radio Shack several decades ago). But YMMV.

Online Resistor Color Code Tool

20 thoughts on “Online resistor code tool

  1. Ryan says:

    Since I started just organizing my resistors or keeping the unused ones in their packaging, I just don’t remember any of the color code.

    I’ve often wondered how many other folks have forgotten the color codes? I used to have it memorized pretty well in school, but now I don’t stand a chance at remembering any of it (and I’m only 29 years old!).

    Are we in the minority here, or are there others out there?

  2. RocketGuy says:

    I got the free resistor code app for the iPhone, so I have it to hand when needed, without having to fire up a browser. It also has a handy series/parallel calculator built in.

    Search for “ResistorCode” in the app store, price is right!

  3. thunderhammer says:

    I’m mildly color blind, and while I can clearly differentiate all of those colors on the screen, on resistors, brown looks like purple, orange looks like red, etc. When I need a specific resistor, I have to spend about 20 minutes with a stack of resistors and a multimeter, or just order 50 of them from mouser or digikey and wait a week.

    You can’t even imagine what a living hell circuits lab was for me in college.

    1. RocketGuy says:

      Just a wacky thought wrt colorblindness, there is a color sensor at sparkfun, perhaps a small arduino based project would be helpful to ID colors?

      I’m thinking something with a small focused aperture or just a small hole you press against the color in question. It has an onboard white led, so aim shouldn’t be too hard.

      More difficult would be parsing the output, but if you could get a average wavelength at least, that might at least give you enough for an educated guess.

      1. Viadd says:

        How about an iPhone/Android/whatever App where you snap a picture of a resistor, or even a bunch of resistors on a circuit board or workbench, and it locates each resistor in the picture, reads off the color code, and annotates the picture with the resistance values.

        “I know there’s a 470k resistor somewhere around here” /click/ “there it is.”

  4. Ryan Kearney says:

    Somehow I think this is a bit easier when it comes to getting resistor codes.

  5. jammit says:

    I would have posted the mnemonic that I use in here, but it’s NSF little children and big babies, so I post a link to Wikipedia. Search for mnemonics

  6. Andy says:

    Who uses through-hole any more?

  7. eric says:

    it would be nice if there was a way to enter codes for 1% tolerance resistors, which are very common. this type often has a blue body, and 5 stripes. There are 3 significant figures, 1 multiplier, and 1 tolerance band.

    The tolerance stripe will be brown if its a 1% resistor… i.e. no gold.
    for example:
    orange white black orange brown
    (390) * (1000) @ 1% tolerance = 390k

    and its funny to see 10% resistors included. I think they stopped making those in the 1970s!

  8. Don Hersey says:

    The blue body is typically associated w/ metalfilm composition. Brown implies carbon composition. Metalfilms are low-noise and low-inductive. High-value Rs are typically metal-oxide. Wirewound resistors are rugged but inductive, unless they are counter-inductively wound. Resistors in the feedback loops of op-amps should be stable if the circuit is to retain precision over time.
    A more recent development is programmable resistors. These can have an i2c interface, and look to be a fun way to automate classic circuits.

Comments are closed.

Discuss this article with the rest of the community on our Discord server!

Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. His free weekly-ish maker tips newsletter can be found at

View more articles by Gareth Branwyn


Maker Faire Bay Area 2023 - Mare Island, CA

Escape to an island of imagination + innovation as Maker Faire Bay Area returns for its 15th iteration!

Buy Tickets today! SAVE 15% and lock-in your preferred date(s).