Resistor Color Code Calculator

Reading resistor color bands

A resistor's value is printed as colored bands. In a 4-band resistor the first two bands are significant digits, the third is a power-of-ten multiplier, and the fourth is the tolerance. 5-band (precision) resistors add a third significant digit; 6-band resistors add a temperature coefficient band.

R = (significant digits) × multiplier

Read the bands from the end where they're grouped closest together. The tolerance band (often gold or silver) is usually set slightly apart and read last.

The color-to-digit code

Each color maps to a digit: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. The same colors act as the power-of-ten multiplier — brown means ×10, red ×100, and so on — while gold and silver as multipliers mean ×0.1 and ×0.01 for values below 10 Ω. As tolerance bands, gold is ±5% and silver ±10%; the precision colors brown (±1%) and red (±2%) appear on 5-band parts. A handy memory aid is that the colors follow the order of the rainbow through the middle of the scale.

Worked example

Take brown-black-red-gold. The first two bands (brown, black) give the digits 1 and 0, so 10; the third band (red) multiplies by 100; the gold band is ±5% tolerance. That's 10 × 100 = 1000 Ω, a 1 kΩ resistor at ±5%. On a 5-band precision version the same value reads brown-black-black-brown-brown: three digits (1, 0, 0), a ×10 multiplier, and ±1%.

Common mistakes

The usual error is reading the bands backwards — start from the grouped end, not the lone tolerance band. Some colors are easy to confuse under poor lighting (red vs. orange, brown vs. red), so when a reading looks odd, measure with a meter or cross-check against thestandard E-series values, since real resistors only come in those preferred numbers.

Reading direction, and what tolerance means

The commonest error decoding a resistor is reading it backwards. Two checks catch it: the tolerance band is usually gold, silver or brown and sits slightly apart from the group, and a value read the wrong way round generally is not astandard value. Worth remembering too that the tolerance band describes manufacturing spread at room temperature — the actual resistance also drifts with temperature at a rate the colour code does not express, which is what the sixth band on a six-band part is for.