Who this is for: Beginners identifying through-hole resistors. You should be comfortable with basic multiplication and the meaning of ohms (Ω), kilo-ohms (kΩ), and mega-ohms (MΩ).
What you will learn: identify the reading direction, interpret digit and multiplier bands, calculate tolerance limits, and check when a color-code reading may be uncertain.
Checked examples: The nominal resistance and tolerance ranges below were checked by direct arithmetic. They describe the marked nominal values, not measurements of a physical component.
Find the reading direction
A common 4-band resistor has two significant-digit bands, a multiplier band, and a tolerance band. A common 5-band resistor has three significant-digit bands, then a multiplier and a tolerance band. Read the bands from the end opposite the tolerance band. The tolerance band is often spaced slightly apart; gold and silver are not used as significant digits.
Do not rely on spacing or color alone if the bands are damaged, faded, or ambiguous. Resistor bodies and band layouts vary. Check the component documentation or measure it when identification matters.
Digit bands
The first two bands of a 4-band resistor, or first three of a 5-band resistor, use these digits:
| Color | Digit |
|---|---|
| Black | 0 |
| Brown | 1 |
| Red | 2 |
| Orange | 3 |
| Yellow | 4 |
| Green | 5 |
| Blue | 6 |
| Violet | 7 |
| Gray | 8 |
| White | 9 |
Multiplier and tolerance bands
Multiply the significant digits by the multiplier. Tolerance gives the possible percentage variation from the nominal value.
| Color | Multiplier | Tolerance |
|---|---|---|
| Black | ×1 | — |
| Brown | ×10 | ±1% |
| Red | ×100 | ±2% |
| Orange | ×1,000 | — |
| Yellow | ×10,000 | — |
| Green | ×100,000 | ±0.5% |
| Blue | ×1,000,000 | ±0.25% |
| Violet | ×10,000,000 | ±0.1% |
| Gray | ×100,000,000 | ±0.05% |
| White | ×1,000,000,000 | — |
| Gold | ×0.1 | ±5% |
| Silver | ×0.01 | ±10% |
| No band | — | ±20% |
The table lists common resistance-code multipliers and tolerance bands. A dash means that the color is not used for that part of this common code.
Worked example: 4 bands
Suppose the bands, read from the significant-digit end, are red, violet, orange, gold:
- Red and violet give the digits 2 and 7, or 27.
- Orange is a ×1,000 multiplier: 27 × 1,000 = 27,000 Ω = 27 kΩ.
- Gold means ±5%. Five percent of 27 kΩ is 1.35 kΩ.
The marked nominal value is 27 kΩ ±5%, so the tolerance range is 25.65 kΩ to 28.35 kΩ. The actual resistance can fall within that range under the component's specified measurement conditions.
Worked example: 5 bands
For brown, black, black, red, brown, the first three bands give 100. Red multiplies by 100, so the nominal value is 100 × 100 = 10,000 Ω, or 10 kΩ. Brown tolerance is ±1%, which gives a range of 9.9 kΩ to 10.1 kΩ.
Try it yourself
A resistor has green, blue, brown, and gold bands. What is its nominal value and 5% tolerance range?
Show the worked answer
Green and blue give 56. Brown multiplies by 10, so the nominal value is 560 Ω. Five percent is 28 Ω, giving a range of 532 Ω to 588 Ω.
Check the component before using it
- Color perception, lighting, aging, and small band spacing can make visual identification uncertain. Do not treat a visual estimate as a precision measurement.
- To measure resistance, disconnect power and isolate at least one resistor lead from the circuit; other circuit paths can affect the reading. Follow the meter and equipment instructions.
- A resistance value alone does not establish a resistor's power rating, voltage rating, temperature behavior, or suitability for a circuit.