Select the color bands to calculate resistance instantly, or flip to reverse mode and enter a resistance value to see the bands you need.
Resistors are too small to print numbers on reliably, so manufacturers use colored bands instead — readable from any angle, even on a component a few millimeters long. Each color stands for a digit, and read together the bands spell out the resistance value in ohms, plus how close to that value the part is guaranteed to be.
Most resistors in hobby kits and general electronics use four bands:
Precision resistors add a third digit band before the multiplier, giving three significant digits instead of two — that's why 5- and 6-band resistors hold tighter tolerances than 4-band ones. When a 6th band is present, it indicates the temperature coefficient: how much the resistance drifts per degree of temperature change, important in precision analog circuits.
| Color | Digit | Multiplier | Tolerance |
|---|
Resistors aren't manufactured at every possible number — they follow standard series like E12 (12 values per decade) so that a manageable set of parts can cover any circuit need. The base E12 values are:
10 · 12 · 15 · 18 · 22 · 27 · 33 · 39 · 47 · 56 · 68 · 82
Multiply any of these by 1, 10, 100, 1k, 10k, and so on to get the full range — 220Ω, 4.7kΩ, and 100kΩ are all E12 values.
Gold and silver almost always appear as the tolerance band, marking ±5% and ±10% respectively. Gold can also serve as a ×0.1 multiplier on some resistors.
Start from the side furthest from the tolerance band. The tolerance band (usually gold or silver, sometimes brown or red on precision parts) is always last and is often spaced slightly apart from the others.
Surface-mount (SMD) resistors use printed numeric codes instead, because they're too small for color bands to be printed or read reliably.
Discussion