Resistor Colour Codes Explained
Through-hole resistors often identify their value using coloured bands rather than printed numbers. A standard 4-band resistor uses two significant digits, a multiplier and a tolerance band.
You can decode one instantly with our Resistor Colour Code Calculator.
The digit colours
Black = 0, brown = 1, red = 2, orange = 3, yellow = 4, green = 5, blue = 6, violet = 7, grey = 8 and white = 9.
Example: brown-black-red-gold
Brown is 1 and black is 0, giving the first two digits 10. Red is the multiplier ×100, so 10 × 100 = 1000 Ω, or 1 kΩ. Gold is ±5% tolerance.
A 1 kΩ ±5% resistor can therefore reasonably measure between 950 Ω and 1050 Ω when new and at the specified conditions.
How to identify the reading direction
The tolerance band is usually separated slightly from the other bands. Gold and silver are commonly used for tolerance, which makes them useful clues for identifying which end to read first.
Common tolerance colours
- Brown: ±1%
- Red: ±2%
- Gold: ±5%
- Silver: ±10%
Precision resistors may use additional bands and tighter tolerances. A 5-band code normally uses three significant digits before the multiplier.
Why a burnt resistor may not be the original fault
In repair work, a visibly burnt resistor often indicates excessive current caused by another failure. Replacing the resistor without checking the surrounding circuit can result in the new part failing again. Shorted semiconductors, leaky capacitors or incorrect supply conditions may be responsible for the overload.
Resistance versus power rating
Colour bands identify resistance and tolerance, not the resistor’s wattage. Power rating depends mainly on resistor construction and physical size. When replacing a resistor, match the resistance and use an appropriate voltage, power and technology rating for the circuit.
Series and parallel combinations
If the exact value is unavailable, resistors can sometimes be combined. Series values add directly. Parallel values produce a resistance lower than the smallest individual resistor. Use our Series & Parallel Resistor Calculator to check the result.
Measuring resistors in circuit
An in-circuit resistance measurement may read low because other circuit paths sit in parallel with the component. Where safe and appropriate, lifting one leg of the resistor isolates it for a more reliable measurement.
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