How to Read Resistor Colour Codes
Most through-hole resistors use coloured bands instead of printed numbers to indicate their resistance value. By learning the resistor colour code, you can quickly determine a resistor's resistance, multiplier, tolerance and, for some resistors, temperature coefficient. Although digital multimeters make measuring resistors easy, understanding colour codes remains an essential skill for anyone working with electronics.
Why Use Colour Bands?
Resistors are often too small to print their values clearly. Colour bands provide a compact and reliable method of identifying resistor values without requiring additional markings.
The colours are internationally standardised, allowing resistors from different manufacturers to be identified consistently.
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% |
Four-Band Resistors
Four-band resistors are the most common type used in general-purpose electronics.
| Band | Meaning |
|---|---|
| Band 1 | First significant digit. |
| Band 2 | Second significant digit. |
| Band 3 | Multiplier. |
| Band 4 | Tolerance. |
Brown Black Red Gold
1 0 ×100 ±5%
= 1,000 Ω
= 1 kΩ ±5%
Five-Band Resistors
Five-band resistors provide greater precision by using three significant digits instead of two.
| Band | Meaning |
|---|---|
| Band 1 | First digit. |
| Band 2 | Second digit. |
| Band 3 | Third digit. |
| Band 4 | Multiplier. |
| Band 5 | Tolerance. |
Brown Black Black Red Brown
1 0 0 ×100 ±1%
= 10,000 Ω
= 10 kΩ ±1%
Six-Band Resistors
Six-band resistors are similar to five-band resistors but include an additional band indicating the temperature coefficient (TCR), usually expressed in parts per million per degree Celsius (ppm/°C).
| Band | Meaning |
|---|---|
| Band 1 | First digit. |
| Band 2 | Second digit. |
| Band 3 | Third digit. |
| Band 4 | Multiplier. |
| Band 5 | Tolerance. |
| Band 6 | Temperature coefficient. |
Temperature Coefficient (TCR)
| Colour | TCR (ppm/°C) |
|---|---|
| Brown | 100 |
| Red | 50 |
| Orange | 15 |
| Yellow | 25 |
| Blue | 10 |
| Violet | 5 |
Reading Tips
- The tolerance band is usually spaced slightly farther from the other bands.
- Gold or silver is commonly the last band.
- If there is no tolerance band, the resistor is typically ±20%.
- Always read from the end opposite the tolerance band.
- When unsure, verify the value with a digital multimeter.
Common Examples
| Colours | Value |
|---|---|
| Brown • Black • Brown • Gold | 100 Ω ±5% |
| Red • Red • Brown • Gold | 220 Ω ±5% |
| Yellow • Violet • Brown • Gold | 470 Ω ±5% |
| Brown • Black • Orange • Gold | 10 kΩ ±5% |
| Yellow • Violet • Yellow • Gold | 470 kΩ ±5% |
| Brown • Black • Green • Gold | 1 MΩ ±5% |
Testing a Resistor
- Read the colour bands and calculate the expected resistance.
- Disconnect power from the circuit.
- Measure the resistor using a digital multimeter.
- Compare the measured value with the expected value.
- Ensure the reading is within the specified tolerance.
Common Mistakes
| Mistake | Solution |
|---|---|
| Reading from the wrong end. | Start from the end opposite the tolerance band. |
| Confusing red and orange. | Use good lighting or a magnifying glass. |
| Ignoring the multiplier band. | Always calculate the multiplier before determining the value. |
| Misreading faded colours. | Measure the resistor with a multimeter. |
Key Points
- Colour bands identify a resistor's value, multiplier and tolerance.
- Four-band resistors are the most common in general-purpose electronics.
- Five-band resistors provide greater precision.
- Six-band resistors include a temperature coefficient.
- A digital multimeter is the quickest way to verify a resistor's value.