# Resistor Color Code Calculator > Read the Bands, or Start From the Value You Need Free resistor color code calculator. Read 3, 4, 5 and 6 band resistors to value, tolerance and TCR. Reverse a value into bands, nearest E24 or E96 and. URL: https://tools.scoreroute.com/tools/resistor-color-code-calculator/ Markdown: https://tools.scoreroute.com/tools/resistor-color-code-calculator/.md ## What Do You Know? 3 band: two digits, no tolerance, so 20 percent. 4 band: two digits plus tolerance. 5 band: three digits plus tolerance. 6 band: three digits plus tolerance plus temperature coefficient. Value accepts 4k7, 4.7k, 4700, 4.7 kOhm, 4.7K or 4.7M. Leave the voltage at 0 to skip the power figures. ### Or size an LED resistor directly Everything is computed in your browser. Nothing is uploaded or stored. ### Why a Chatbot Gets This Wrong More Often Than It Should Ask a language model to read a resistor and it will usually give you a number. The number is often right. The reason it is often right is the same reason it is sometimes wrong by a factor of ten: the model has memorised thousands of worked examples, and the mapping from bands to value is not one rule but three rules read in sequence, plus a handful of exceptions nobody mentions in a training paragraph. The three rules are: the digit bands form a number, the multiplier band is a separate power of ten, and the tolerance band is a percentage of the result. The failure mode is collapsing the first two. A band order of violet, green, yellow, gold is 7, 5, times 10000, 5 percent, so 750 kOhm. Read the multiplier one place to the left and you get 75 kOhm, which is a real resistor, the right shape, the right tolerance, and the wrong part. Nothing in the answer looks wrong. The second thing a language model will not volunteer is the size of the error. A 5 percent part is not 5 percent accurate in a way that is easy to ignore: 1 kOhm at 5 percent is 950 to 1050 ohms, a 100 ohm window. For a resistor setting an op-amp gain that is a design change. For a current limit it is fine. The same marking means opposite things in those two circuits, and a tool that prints the ohm range tells you which one you are in. The third is power. The arithmetic is one line, P equals V squared over R, and the consequence is the part that matters. 5 V across 1 kOhm is 0.025 W, so the calculation says any resistor will do, and a quarter watt part is on the shelf. But 12 V across the same 1 kOhm is 0.144 W, which is over half of a quarter watt part, and running a resistor continuously above its rating does not fail cleanly. It drifts out of tolerance, discolours, and eventually opens. A 5 V rail that measures 5.25 V, or a 9 V alkaline that has dropped to 6 V, is enough to move you into that band without changing a single component. ### What You Get - **3, 4, 5 and 6 bands, all four layouts** — the right bands get the right jobs, including the 6 band temperature coefficient, and each band is labelled with what it contributed rather than just being coloured. - **The tolerance as a real ohm range** — 950 to 1050 ohms, not just the number 5. - **Temperature drift from the TCR band** — what the resistance actually becomes at a temperature you choose, which is usually the reason a 6 band part was specified at all. - **The reverse direction** — enter the value you need and get the bands to buy, in both 4 band and 5 band form, so you are not forced into a precision part you do not need. - **Nearest E24 and nearest E96** — the two series that cover almost all real purchases, with the error each one leaves you. - **Power and a recommended rating** — dissipation at the voltage you entered, and the next standard size to fit, with the headroom spelled out. - **LED mode** — supply voltage, forward voltage and target current in milliamps to one resistor, snapped to something buyable. - **The current IEC tolerance table** — including the yellow 0.02 percent and grey 0.01 percent bands added in IEC 60062:2016, which most published charts still predate. ### Reading It Backwards, Which Is the Part Nobody Does Decoding a resistor is only half the job, and it is the half that is already everywhere. The question you actually have in front of you is usually the other direction: the circuit wants 4.7 kOhm, and now what do you put on the board. That has three answers, not one, and they do not agree. The first is whether 4.7 kOhm is even a value you can buy. 4.7 is in E12 and E24, so a 4.7 kOhm 5 percent part is a 1 percent part in a brown, violet, red, gold body: 47 times 100. If you need something closer, 4.70 kOhm and 4.65 kOhm are E96, and a 4.65 kOhm 1 percent part is a five band part: 4, 6, 5, times 10, brown. The two are physically different parts with different prices, and nothing in a chatbot answer tells you which one you are holding. The second is power, and the rule of thumb worth knowing is that you want at least twice the calculated dissipation. Doubling is not superstition and it is not conservative either, it is what keeps ambient temperature, supply tolerance and part ageing from combining to push you past the rating. Read that as a ceiling on what each size may dissipate: a 0.125 W part covers 62.5 mW, a 0.25 W part covers 125 mW, a 0.5 W part covers 250 mW. So 0.03 W and 0.06 W both land on 0.125 W, 0.07 W pushes to 0.25 W, 0.12 W is still 0.25 W, and 0.13 W needs 0.5 W. The steps are where the money is. The third is the error the chosen value leaves you, which is not the same as the tolerance band on the part. A 4.65 kOhm part against a 4.700 kOhm target is 1.06 percent low from the choice of value alone, before the part's own 1 percent tolerance is applied at all. Snapping to a preferred value and specifying a tolerance are two separate decisions and they stack. ### What This Tool Will Not Tell You It reads what the bands say. It cannot tell you what is actually on the part, which is what a multimeter is for. Colour bands fade, dirt gets into the gap between bands, and on a cheap part the paint is not always where the standard says it is. A reading that disagrees with the bands is information about the part, not about the calculator. It also cannot tell you the reading direction from the bands alone, because the code is not self-describing in that respect. Gold and silver always sit at the tail end, since neither can be a significant digit, and a tolerance band is often printed wider or with a bigger gap before it. A 4 band resistor whose multiplier is gold or silver is one of the two cases where orientation is obvious, and outside that you are looking for the wider tolerance band or the bigger gap. If a decode gives you a value that is absurd, read it from the other end before you trust it. Standard 0.1 percent and 0.01 percent parts are usually E192 and surface mount, not colour banded, so the band scheme itself is a 5 percent era format being asked to express precision it was not built for. When a design needs more than E96, the answer is a precision part with a printed code, not a cleverer colour reading. ### The Full Colour Table Every figure below is IEC 60062:2016. Tolerance in percent, the letter that goes with it, and the temperature coefficient in ppm per K are each band specific, and a colour is not the same number in all three columns. Green is 5 as a digit, 0.5 percent as a tolerance and 20 ppm per K as a temperature coefficient. The table scrolls sideways on a narrow screen rather than pushing the page wider than the screen. ### Frequently Asked **How do I read a 4 band resistor color code?** Read left to right. The first band is the first significant digit and the second is the second significant digit, so brown then black means 10. The third band is the multiplier, a power of ten: black is times 1, brown times 10, red times 100, up through grey times 100 million, with gold times 0.1 and silver times 0.01 for values below 10 ohms. The fourth band is the tolerance, the percentage the real resistance may differ by. Red violet yellow gold is 2, 7, then times 10000, so 270000 ohms, or 270 kilohms, at plus or minus 5 percent. The digits and the multiplier are separate jobs and mixing them up is the single most common way to read a resistor wrong by a factor of ten. **What is the difference between a 4 band and a 5 band resistor?** One extra significant digit. A 4 band resistor gives two significant digits, so 47 followed by the multiplier can only express 47 times something, and 4.7 kOhm is the closest a 4 band part can get. A 5 band resistor gives three significant digits, so 4.70 kOhm is exact. That is why 1 percent and 0.1 percent parts are almost always 5 band, and why a 4 band resistor can never be more accurate than about 1 percent no matter which tolerance colour is on it. The multiplier moves one place to the right when you add the third digit, because the significant digits and the multiplier are a fixed number of characters. **What is the last band on a 6 band resistor?** The temperature coefficient of resistance, written as ppm per degree Celsius, which is how much the resistance changes per degree away from the reference temperature of 25 C. A black sixth band is 250 ppm per K, brown is 100, red is 50, yellow is 25, green is 20, orange is 15, blue is 10, violet is 5 and grey is 1. A 100 ppm per K part sitting 55 degrees above 25 C is about 0.55 percent off its marked value, which is less than its own 1 percent tolerance band and therefore usually irrelevant. Precision parts are the exception: 15 or 5 ppm per K over the same 55 degrees is 0.08 or 0.03 percent, and that is often the whole reason the part was specified. **What resistor do I use as an LED current limiting resistor?** Take the supply voltage minus the LED forward voltage, divide by the current you want, and that is the resistance. A red LED with a 2 V forward voltage on a 5 V supply running at 10 mA needs 3 divided by 0.01, which is 300 ohms. Then snap it to a value you can actually buy, because 300 ohms is not a standard value, and check the power. 300 ohms at 3 V dissipates 0.03 W, so the smallest part that fits with headroom is a one eighth watt 0.125 W resistor. The mistake that kills LEDs is skipping the power step and picking a part too small for the voltage, or ignoring that a 9 V alkaline falls to about 6 V and a 5 V USB supply can sit at 5.25 V, both of which push more current through the LED than the calculation at the nominal voltage suggests. **Why does the tolerance colour chart on this page differ from older ones?** IEC 60062:2016 added two tolerance bands that most charts published before 2016 do not have: yellow is plus or minus 0.02 percent and grey is plus or minus 0.01 percent. Before that revision, yellow and grey rings were not assigned these meanings, and grey was sometimes used informally for plus or minus 0.05 percent. A separate long standing practice is that some high voltage resistor makers use yellow and grey where gold and silver would go, to keep metal pigment out of the lacquer, so a yellow band on an old high voltage part can mean plus or minus 5 percent. The charts that still say grey is 0.05 percent are not wrong for the parts they were written for, they are just older than the current standard. **What does a 0 ohm jumper resistor do?** It is a single black band and it is nominally zero ohms, used to bridge a footprint so a board assembles the same way whether or not that circuit is populated. It is not exactly zero. A typical 0 ohm jumper is rated 1 percent with a 250 ppm per K temperature coefficient, so it can be a few milliohms and it drifts with temperature exactly like any other resistor. That is why you never treat a jumper as a dead short in a design, and why it cannot substitute for a real resistance in a current setting network. **Is my data uploaded or stored anywhere?** Nothing leaves your browser. The decoding, the E series search and the power arithmetic all run as JavaScript on your own machine, there is no request to a server, no account, and nothing written to disk or to any database. Reload the page and it is all gone. #### Related Tools - [Unit Converter](/tools/unit-converter/) - [Size Converter](/tools/size-converter/) - [Barcode Generator](/tools/barcode-generator/) - [Color Palette Generator](/tools/color-palette-generator/) ## References - [BIPM — SI Brochure (The International System of Units)](https://www.bipm.org/en/publications/si-brochure) - [IANA — Character Sets](https://www.iana.org/assignments/character-sets/character-sets.xhtml)