Resistor Colour Code
Most through-hole resistors use coloured bands instead of printed numbers. These coloured bands indicate the resistor's resistance value, tolerance and, in some cases, its temperature coefficient.
Why Use Colour Bands?
Resistors are often too small to print numerical values directly onto the body.
Instead, manufacturers use coloured bands that can be read quickly once the colour code is understood.
The Colour Code Table
| Colour | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1,000 | — |
| Yellow | 4 | ×10,000 | — |
| Green | 5 | ×100,000 | ±0.5% |
| Blue | 6 | ×1,000,000 | ±0.25% |
| Violet | 7 | ×10,000,000 | ±0.1% |
| Grey | 8 | ×100,000,000 | ±0.05% |
| White | 9 | ×1,000,000,000 | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
| No Band | — | — | ±20% |
Reading a 4-Band Resistor
A four-band resistor contains:
- First significant digit.
- Second significant digit.
- Multiplier.
- Tolerance.
Example:
Brown – Black – Red – Gold
- Brown = 1
- Black = 0
- Red = ×100
- Gold = ±5%
Resistance:
10 × 100 = 1000 Ω = 1 kΩ ±5%
Reading a 5-Band Resistor
Five-band resistors provide greater accuracy.
- First digit.
- Second digit.
- Third digit.
- Multiplier.
- Tolerance.
Example:
Brown – Black – Black – Brown – Brown
- 1
- 0
- 0
- ×10
- ±1%
Result:
100 × 10 = 1000 Ω = 1 kΩ ±1%
Reading a 6-Band Resistor
A six-band resistor is similar to a five-band resistor but includes an additional band representing the temperature coefficient (ppm/°C).
These resistors are commonly used in precision measuring instruments and laboratory equipment.
Tolerance
Tolerance indicates how close the actual resistance is to its stated value.
| Band | Tolerance |
|---|---|
| Brown | ±1% |
| Red | ±2% |
| Green | ±0.5% |
| Blue | ±0.25% |
| Violet | ±0.1% |
| Grey | ±0.05% |
| Gold | ±5% |
| Silver | ±10% |
| No Band | ±20% |
Helpful Memory Aid
Many students use memory phrases to remember the order of the colours.
A simple approach is simply to memorise the sequence:
Black → Brown → Red → Orange → Yellow → Green → Blue → Violet → Grey → White
With practice, reading resistor values becomes almost automatic.
Common Mistakes
- Reading the resistor from the wrong end.
- Confusing red with orange.
- Ignoring the tolerance band.
- Forgetting to apply the multiplier.
- Misidentifying faded colour bands.
Practical Tips
- Read from the end where the bands are closest together.
- The tolerance band is usually spaced farther from the others.
- Use a multimeter to verify the resistance if uncertain.
- Good lighting helps distinguish similar colours.
- Precision resistors often use five or six bands.
Key Points
- Colour bands indicate resistor values.
- Four-band resistors use two significant digits.
- Five-band resistors use three significant digits.
- The multiplier determines the final resistance value.
- The last band usually indicates tolerance.
- Six-band resistors include temperature coefficient information.