Resistor Color Coding
To distinguish left from right there is a gap between the C and D bands.
- band A is first significant figure of component value (left side)
- band B is the second significant figure
- band C is the decimal multiplier
- band D if present, indicates tolerance of value in percent (no band means 20%)
For example, a resistor with bands of yellow, violet, red, and gold will have first digit 4 (yellow in table below), second digit 7 (violet), followed by 2 (red) zeros: 4,700 ohms. Gold signifies that the tolerance is ±5%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms.
Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability); refer to MIL-HDBK-199 for further details.
Tight tolerance resistors may have three bands for significant figures rather than two, or an additional band indicating temperature coefficient, in units of ppm/K.
All coded components will have at least two value bands and a multiplier; other bands are optional.
The standard color code per EN 60062:2005 is as follows:
| Color | Significant figures |
Multiplier | Tolerance | Temp. Coefficient (ppm/K) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Black | 0 | ×100 | – | 250 | U | |||||
| Brown | 1 | ×101 | ±1% | F | 100 | S | ||||
| Red | 2 | ×102 | ±2% | G | 50 | R | ||||
| Orange | 3 | ×103 | – | 15 | P | |||||
| Yellow | 4 | ×104 | (±5%) | – | 25 | Q | ||||
| Green | 5 | ×105 | ±0.5% | D | 20 | Z | ||||
| Blue | 6 | ×106 | ±0.25% | C | 10 | Z | ||||
| Violet | 7 | ×107 | ±0.1% | B | 5 | M | ||||
| Gray | 8 | ×108 | ±0.05% (±10%) | A | 1 | K | ||||
| White | 9 | ×109 | – | – | ||||||
| Gold | – | ×10-1 | ±5% | J | – | |||||
| Silver | – | ×10-2 | ±10% | K | – | |||||
| None | – | – | ±20% | M | – | |||||
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Resistors use preferred numbers for their specific values, which are determined by their tolerance. These values repeat for every decade of magnitude: 6.8, 68, 680, and so forth. In the E24 series the values are related by the 24th root of 10, while E12 series are related by the 12th root of 10, and E6 series by the 6th root of 10. The tolerance of device values is arranged so that every value corresponds to a preferred number, within the required tolerance.
Zero ohm resistors are made as lengths of wire wrapped in a resistor-shaped body which can be substituted for another resistor value in automatic insertion equipment. They are marked with a single black band.
The 'body-end-dot' or 'body-tip-spot' system was used for radial-lead (and other cylindrical) composition resistors sometimes still found in very old equipment; the first band was given by the body color, the second band by the color of the end of the resistor, and the multiplier by a dot or band around the middle of the resistor. The other end of the resistor was colored gold or silver to give the tolerance, otherwise it was 20%.
Extra bands on ceramic capacitors will identify the voltage rating class and temperature coefficient characteristics. A broad black band was applied to some tubular paper capacitors to indicate the end that had the outer electrode; this allowed this end to be connected to chassis ground to provide some shielding against hum and noise pickup.
Polyester film and "gum drop" tantalum electrolytic capacitors are also color coded to give the value, working voltage and tolerance.
Read more about this topic: Electronic Color Code
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