Resistor color code calculator
| Colour | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1k | — |
| Yellow | 4 | ×10k | — |
| Green | 5 | ×100k | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Violet | 7 | ×10M | ±0.1% |
| Grey | 8 | ×100M | ±0.05% |
| White | 9 | ×1G | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Brown-black-red-gold is 1 kΩ at ±5%: brown is 1, black is 0, red multiplies by 100, gold is the tolerance. Four-band resistors use two significant digits; five and six band use three, with the sixth giving temperature coefficient.
How to read a resistor
The colour code exists because a resistor is too small to print a number on legibly, and it survives because it can be read from any angle. Its weaknesses are well known: brown, red and orange are hard to tell apart under warm light, and on a 4-band resistor with no clear tolerance band it is genuinely ambiguous which end to start from. The rule of thumb is that the tolerance band sits slightly further from its neighbours, and that a reading which produces a nonsense value: 47 MΩ where a pull-down should be; means you read it backwards.
Questions
The tolerance band is usually gold or silver and sits slightly apart from the others. Put it on the right.
A ±20% tolerance. It is rare on modern parts but common on old stock.
Four band gives two significant digits; five gives three, for tighter values like 4.99 kΩ.
Temperature coefficient in parts per million per degree; brown is 100 ppm, red 50, blue 10.
Because they genuinely do under warm lighting on a small part. Use daylight, or measure it.