Resistors

Reading resistor color codes

Most through-hole resistors don't print their value — they use colored bands instead. This tool converts those bands into a resistance in ohms and a tolerance, and it works in reverse too: enter a resistance and it shows you the bands to look for.

How the bands work

Each color maps to a number: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. On a standard 4-band resistor, the first two bands are digits, the third is a multiplier (how many zeros to add), and the fourth is the tolerance — usually gold (±5%) or silver (±10%). A 5-band resistor adds a third digit for tighter-tolerance parts, and a 6-band adds a temperature-coefficient band on the end.

Using the tool

Pick the number of bands, then set each band's color. The resistance, tolerance, and value range update as you go.

Common question

Which end do I read from?

Read from the end opposite the tolerance band. Gold and silver are only ever tolerance or multiplier colors, so if you see one, that end is the finish — put it on the right and read the other direction. The tolerance band is also often set slightly apart from the rest.