Resistor Color Code Calculator
Decode resistor color bands to find resistance in ohms and tolerance.
Supports 4-band and 5-band resistors with the full color table and E12/E24/E96 series.
Resistor color codes are a standardized system for marking resistance values, tolerance, and temperature coefficient on small resistors where printing numbers is impractical. Each colored band represents a digit, multiplier, or tolerance value. Reading color codes is a fundamental electronics skill.
Resistance value formula (4-band resistor): Resistance = (Band1 × 10 + Band2) × 10^Band3
5-band resistor formula: Resistance = (Band1 × 100 + Band2 × 10 + Band3) × 10^Band4
Where each band’s color maps to a number:
Color code table:
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | n/a |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1k | n/a |
| Yellow | 4 | ×10k | n/a |
| Green | 5 | ×100k | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Violet | 7 | ×10M | ±0.1% |
| Grey | 8 | n/a | ±0.05% |
| White | 9 | n/a | n/a |
| Gold | n/a | ×0.1 | ±5% |
| Silver | n/a | ×0.01 | ±10% |
Read “n/a” as “that colour is never used in that position”. Black has no tolerance meaning, and gold and silver are never digits. A resistor with no tolerance band at all is ±20%, which you will only meet on very old stock.
Tolerance band meaning: The final band indicates how much the actual resistance may deviate from the stated value. A 1kΩ resistor with ±5% tolerance can be anywhere from 950Ω to 1,050Ω.
Which way round do you read it? This is the part that actually trips people up, not the colours. The tolerance band is usually gold or silver, and it sits slightly further from the others with a wider gap before it. If both ends look identical, check for a colour that cannot be a first digit: gold, silver, or black at one end means that end is the tail. Get it backwards and brown-black-red (1 kΩ) reads as red-black-brown, which is 200 Ω.
Standard values and why yours might not be one Resistors are not made in every value. The E12 series has 12 values per decade (1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2), and E24 doubles that with 1.1, 1.3, 1.6, 2.0, 2.4, 3.0, 3.6, 4.3, 5.1, 6.2, 7.5 and 9.1. E96 (1% parts) has 96 steps and includes values like 4.75 and 6.98 that need three digit bands, which is why precision resistors are 5-band. If the calculator decodes something that is not in any of these series, you have almost certainly misread a band.
Worked example: 4-band resistor: Bands: Yellow, Violet, Red, Gold
- Band 1 (Yellow): 4
- Band 2 (Violet): 7
- Band 3 (Red): multiplier ×100
- Band 4 (Gold): tolerance ±5%
Resistance = (4 × 10 + 7) × 100 = 47 × 100 = 4,700 Ω = 4.7 kΩ ±5%
Actual range: 4,700 × 0.95 to 4,700 × 1.05 = 4,465 Ω to 4,935 Ω. For precision circuits, use brown-band (1%) or better resistors to keep actual resistance close to the nominal value.
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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