Through-hole resistors print their value as coloured bands. This calculator decodes the common 4-band scheme: pick each band’s colour and read the resistance in ohms (or kΩ / MΩ) with its tolerance — handy for electronics hobbyists, students, and anyone repairing a board.
How it works
In a 4-band resistor the first two bands are significant digits, the third is a multiplier (a power of ten), and the fourth is the tolerance. The colours map to numbers in a fixed sequence (black 0 through white 9). The resistance is:
(digit1 × 10 + digit2) × 10^multiplier
Gold and silver are special multipliers (×0.1 and ×0.01) and tolerance values (±5% and ±10%). The tool combines your band selections with this mapping and formats the value in the cleanest unit.
Example
Bands brown, black, red, gold:
- Brown = 1, black = 0 → significant digits 10
- Red multiplier = ×10² = ×100
- 10 × 100 = 1,000 Ω = 1 kΩ
- Gold tolerance = ±5%
| Colour | Digit | Multiplier |
|---|---|---|
| Black | 0 | ×1 |
| Brown | 1 | ×10 |
| Red | 2 | ×100 |
| Orange | 3 | ×1k |
| Yellow | 4 | ×10k |
| Gold | – | ×0.1 (±5%) |
| Silver | – | ×0.01 (±10%) |
All decoding happens locally in your browser; nothing is sent anywhere.