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First year Basic circuits Free · works offline once loaded

Resistor colour code calculator

Pick the bands from left to right — start from the end the bands crowd toward, with the gold or silver band on the right. The drawing follows your picks, and you get the value, the tolerance and the range a good part should measure.

Number of bands
—

Resistance—
Tolerance—
Should measure—

Measure out of circuit, hands off the leads. Some newer charts (IEC 60062:2016) give grey as ±0.01 % — check the maker’s datasheet on a precision part.

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How it works

Each colour stands for a digit, 0 to 9: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. The first two bands (three on a 5-band part) are the significant digits. The next band is the multiplier — how many zeros to add, or gold ×0.1 and silver ×0.01 for values under 10 Ω. The last band is the tolerance: how far from the marked value the real part is allowed to be.

Remember the order

The old trade mnemonic is fine, but the order is also a rainbow with black and brown in front and grey and white at the back: B B R O Y G B V G W.

Worked examples

Yellow, violet, red, gold

  1. Digits: yellow 4, violet 7 → 47.
  2. Multiplier: red is ×100 → 47 × 100 = 4,700 Ω = 4.7 kΩ.
  3. Tolerance: gold ±5 %. 5 % of 4,700 is 235, so a good part measures 4,465 to 4,935 Ω.

Brown, black, black, red, brown (5 band)

  1. Digits: brown 1, black 0, black 0 → 100.
  2. Multiplier: red ×100 → 10,000 Ω = 10 kΩ.
  3. Tolerance: brown ±1 % → 9,900 to 10,100 Ω.

Questions people ask

Which end do I start reading from?

The end the bands are bunched toward. The tolerance band — usually gold or silver — sits on its own at the other end, often with a wider gap in front of it. If a band sits hard against one end, that end is the start. Turn the resistor so the tolerance band is on your right and read left to right.

What is the difference between a 4-band and a 5-band resistor?

Four bands give two digits, a multiplier and a tolerance; five bands give three digits, so the value can be stated more precisely — which is why five-band parts are usually the ±1 % and tighter ones. The multiplier and tolerance bands work the same way on both.

My meter reads a bit different from the colour code. Is it bad?

Not if the reading is inside the tolerance range this calculator shows. A 4.7 kΩ ±5 % part is good anywhere from 4,465 to 4,935 Ω. Measure it out of circuit — anything else connected across it changes the reading — and with your fingers off both leads, because your body is a resistance too.

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