Rule of thumb · ElectricalNº 140 / 167

Resistor bands read digit-digit-multiplier

On a 4-band resistor: first two bands are significant digits, third is the power-of-ten multiplier, fourth is tolerance.

Why it works

IEC 60062 colour code. Gold/silver as the third band means 0.1/0.01 multipliers; as the fourth they mean 5%/10% tolerance.

When it fails

Not on a 5- or 6-band part, where three bands are significant digits and the multiplier moves along. Worse, a 5-band resistor read as a 4-band one gives a plausible wrong value rather than nonsense — and reading the colours from the wrong end does the same.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

Open Resistor Colour Code Calculator →

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How do you read resistor colour bands?

On a 4-band resistor: first two bands are significant digits, third is the power-of-ten multiplier, fourth is tolerance. IEC 60062 colour code.

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