How Resistor Colour Codes Work
Resistor colour codes were standardised to allow resistance values and tolerances to be identified even when the text is too small to read, the resistor is mounted at an angle, or lighting is poor. The system was introduced in the 1920s and remains the universal standard for through-hole resistors worldwide.
Colour Values Table
| Colour | Digit | Multiplier | Tolerance |
|---|
| Black | 0 | ×1 (10⁰) | — |
| 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 | ×0.01 | ±0.05% |
| White | 9 | ×0.1 | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
4-Band Resistors
The most common type for general-purpose resistors (E12 and E24 series, ±5% and ±10% tolerance).
- Band 1: First significant digit
- Band 2: Second significant digit
- Band 3: Multiplier (power of 10)
- Band 4: Tolerance (Gold = ±5%, Silver = ±10%)
Reading: Value = (10 × Digit1 + Digit2) × Multiplier
5-Band Resistors
Used for precision resistors (E96 series, ±1% and ±2% tolerance).
- Band 1: First significant digit
- Band 2: Second significant digit
- Band 3: Third significant digit
- Band 4: Multiplier
- Band 5: Tolerance (Brown = ±1%, Red = ±2%)
Reading: Value = (100 × D1 + 10 × D2 + D3) × Multiplier
Memory Aid (Mnemonic)
"Bad Boys Race Our Young Girls But Violet Generally Wins"
Black · Brown · Red · Orange · Yellow · Green · Blue · Violet · Grey · White
Worked Example — 4-Band
Q: Decode the resistor with bands: Yellow, Violet, Red, Gold
- Band 1 — Yellow = 4
- Band 2 — Violet = 7
- Band 3 — Red = ×100
- Band 4 — Gold = ±5%
- Value = (10×4 + 7) × 100 = 47 × 100 = 4,700 Ω = 4.7 kΩ ±5%
- Range: 4,465 Ω to 4,935 Ω
Worked Example — 5-Band
Q: Decode: Red, Red, Black, Brown, Brown
- Band 1 — Red = 2
- Band 2 — Red = 2
- Band 3 — Black = 0
- Band 4 — Brown = ×10
- Band 5 — Brown = ±1%
- Value = (100×2 + 10×2 + 0) × 10 = 220 × 10 = 2,200 Ω = 2.2 kΩ ±1%
SMD Resistor Codes
Surface-mount resistors (SMD) use a printed code rather than colour bands. 3-digit code: first two digits are significant figures, third is the multiplier power of 10. Example: "472" = 47 × 10² = 4,700 Ω. 4-digit code: three significant figures + multiplier. Example: "4702" = 470 × 10² = 47,000 Ω. The letter "R" denotes the decimal point: "4R7" = 4.7 Ω.
Frequently Asked Questions
How do I read a 4-band resistor colour code?
Hold the resistor with the tolerance band (Gold or Silver) on the right. Read left to right: Band 1 = first digit, Band 2 = second digit, Band 3 = multiplier (number of zeros to add), Band 4 = tolerance. Multiply (10 × Digit1 + Digit2) by the multiplier. Example: Red, Red, Orange, Gold = (10×2 + 2) × 1000 = 22,000 Ω = 22 kΩ ±5%.
What is the colour code for a 470 Ω resistor?
470 Ω has digits 4 and 7, multiplied by 10: Yellow (4), Violet (7), Brown (×10), Gold (±5%). The range is 446.5 Ω to 493.5 Ω. This is a very common resistor value used in LED current-limiting circuits, voltage dividers, and pull-up/pull-down configurations.
What does the gold band mean on a resistor?
Gold means different things depending on position. As the tolerance band (last band of a 4-band or 5-band resistor): Gold = ±5% tolerance — the actual value is guaranteed within 5% of stated value. As a multiplier band: Gold = ×0.1, meaning a fractional multiplier (e.g., a value like 4.7 Ω: Yellow, Violet, Gold).
How is a 5-band resistor different from a 4-band?
A 5-band resistor encodes three significant digits instead of two, enabling more precise values. The bands are: D1, D2, D3, Multiplier, Tolerance. Value = (100×D1 + 10×D2 + D3) × Multiplier. 5-band resistors are typically ±1% (Brown tolerance) or ±2% (Red tolerance) and are standard for precision analogue circuits, audio equipment, and measurement instruments.
What is the mnemonic for resistor colour codes?
"Bad Boys Race Our Young Girls But Violet Generally Wins" — representing Black(0), Brown(1), Red(2), Orange(3), Yellow(4), Green(5), Blue(6), Violet(7), Grey(8), White(9). Remember that Gold and Silver are only used for multiplier and tolerance bands, not for digit bands.
Why do some resistors have no colour bands?
Surface-mount device (SMD) resistors are too small for colour bands — they use a printed numeric or alphanumeric code. A 3-digit code like "103" means 10 × 10³ = 10,000 Ω. A 4-digit code like "1002" means 100 × 10² = 10,000 Ω. The "R" notation is used for sub-10 Ω values: "4R7" = 4.7 Ω.
How accurate is a gold-band ±5% resistor?
A ±5% tolerance means the actual resistance is within 5% of the stated value. For a 10 kΩ resistor: actual value is between 9,500 Ω and 10,500 Ω. For most digital circuits, ±5% is perfectly adequate. For precision analogue work (oscillators, filters, measurement circuits), use ±1% (Brown, 5-band) or ±0.1% (Violet, 5-band) resistors.