Decode 4, 5, or 6 band resistor colors to get resistance value. Also works in reverse.
A resistor is a passive component that limits or shapes current flow, and resistor identification refers to the process of matching the physical part on a board to its intended electrical value. This matters in troubleshooting because the same circuit can behave very differently when a similar-looking resistor carries the wrong multiplier or tolerance band.
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 Ω | - |
| Brown | 1 | ×10 Ω | ±1% |
| Red | 2 | ×100 Ω | ±2% |
| Orange | 3 | ×1 kΩ | - |
| Yellow | 4 | ×10 kΩ | - |
| Green | 5 | ×100 kΩ | ±0.5% |
| Blue | 6 | ×1 MΩ | ±0.25% |
| Violet | 7 | ×10 MΩ | ±0.1% |
| Gray | 8 | ×100 MΩ | ±0.05% |
| White | 9 | ×1 GΩ | - |
| Gold | - | ×0.1 Ω | ±5% |
| Silver | - | ×0.01 Ω | ±10% |
The first two bands are digits, the third is the multiplier, and the fourth is tolerance. For example: Brown-Black-Red-Gold = 10 × 100 = 1000Ω (1kΩ) ±5%
4-band: 2 digits + multiplier + tolerance. 5-band: 3 digits + multiplier + tolerance (more precision). 6-band: same as 5-band plus temperature coefficient.
Start from the end with bands closest together, or the end without the metallic (gold/silver) tolerance band. The tolerance band is usually slightly separated from the others.
On some six-band resistors, the final band defines how much the resistance changes with temperature, usually expressed in parts per million per degree Celsius.
Use the band decoder for identification, then compare the result with the BOM and measure the part when the application is sensitive to tolerance or field replacement mistakes.