How the resistor color code works
Through-hole resistors are too small to print numbers on, so their value is shown as colored bands. Each color maps to a digit; together they encode the resistance and its manufacturing tolerance, defined by the international standard IEC 60062.
4-band: (d1 d2) × multiplier ± tolerance
5-band: (d1 d2 d3) × multiplier ± tolerance
A 4-band resistor uses two significant digits; a 5-band (precision) resistor uses three. The multiplier is a power of ten, and the final band gives the tolerance — how far the real value may stray from the marked one.
Worked example
A 4-band resistor with bands Brown, Black, Red, Gold:
Brown = 1, Black = 0 → digits "10".
Red = ×100 → 10 × 100 = 1,000 Ω = 1 kΩ.
Gold = ±5% → the real value is between 950 and 1,050 Ω.
The full color chart
| Color | 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 | — | ±0.05% |
| White | 9 | — | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Reading direction and practical tips
- Which end is first? The tolerance band (usually gold or silver) sits slightly apart from the rest, at the end of the resistor. Hold the resistor with that band on the right and read left to right.
- No gold or silver? A precision resistor's tolerance band may be brown or red. The grouping — a wider gap before the last band — still tells you the reading direction.
- Faded colors. Heat and age dull the bands; red can look orange or brown. When in doubt, measure with a multimeter — the code is the nominal value, the meter is the truth.
- Preferred values. Resistors come in standard "E-series" values (E12, E24...), so a decoded value like 4.7 kΩ or 2.2 kΩ is normal, while an odd value may mean you've misread a band.
Tip: once you know the resistance, pair it with the Ohm's Law calculator to find current and power in your circuit.