Resistor colour code
Bands to a value, or a value to bands. Three, four, five or six of them — and miscounting them is a factor of ten thousand. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
Which band means what depends on how many there are
| 3 bands | digit, digit, multiplier. Tolerance is ±20% by default. |
|---|---|
| 4 bands | digit, digit, multiplier, tolerance. |
| 5 bands | digit, digit, digit, multiplier, tolerance. |
| 6 bands | as 5, plus a temperature coefficient. |
So the same four colours mean different things depending on whether there is a fifth. Red-red-black- orange read as four bands is 22 Ω; read as five it is 220 kΩ — ten thousand times more, with nothing on the part to say which it is. Count the bands before you read them, and if the body colour or the spacing does not make the tolerance band obvious, measure it.
The chart on the workshop wall is out of date
This page uses IEC 60062:2016, in which orange, yellow and grey all have tolerances — ±0.05%, ±0.02% and ±0.01% — and pink is a multiplier of one thousandth. Most published charts leave those cells blank because the older editions did.
Not every value can be written
Four bands carry two significant figures and five carry three, so 1,847 Ω has no code. That is not a limitation of the colour system; it is the same fact as the E series. Resistors are made at preferred values, the code was designed to write preferred values, and anything else is a number you calculated rather than a component you can hold.
Reading them the right way round
The tolerance band is usually gold or silver, and gold and silver never appear as digits — so if one end is gold, that end is the last band. Failing that, the tolerance band is often set slightly apart from the rest, or the first band is nearer the end of the body. If none of that helps, a multimeter settles it in two seconds and a misread resistor does not.
What it will not do
- It will not read a photograph. Colour under a workshop light is exactly the problem — brown and red, and orange and yellow, are the pairs that get confused, and a camera makes it worse.
- It will not do capacitor or inductor codes, which are different systems using digits rather than colours.
- It will not do SMD resistor codes — the three- and four-digit and EIA-96 markings on surface-mount parts.