Resistor Color Code Calculator

Reading the bands

Hold the resistor with the gold or silver band on the right. The bands then read left to right: two digits (three on a 5-band part), a multiplier, and the tolerance. Red-red-black-brown-gold is 220 × 10 = 2.2 kΩ at 5%.

The tricks that help

When no band is obviously gold, the tolerance band usually stands a little apart from the rest. Brown, red, orange, yellow count 1-2-3-4 in rainbow order, which covers most of what you'll meet. And when the light is bad, red and orange are genuinely hard to tell apart on a dusty part: a multimeter settles it faster than squinting.

Four bands, five bands and six

Four bands mean two significant digits and 5% or 10% tolerance, the everyday hobby part. Five bands mean three digits and usually 1%, which is what metal film parts need to express values like 4.53 kΩ. A sixth band, set slightly apart, is the temperature coefficient in parts per million per degree, which matters in a reference divider and nowhere else in a typical project.

When the bands lie

Heat discolours a resistor body, and a part that has been running hot can turn a red band brown or a brown band black. If a decoded value looks wrong for the circuit, it probably is: measure the part out of circuit before believing the colours. Old carbon composition resistors also drift upward with age, so a 40-year-old radio full of parts reading 20% high is behaving exactly as expected rather than being mismarked.