Resistor colour code calculator
Value to colours
This calculator converts resistor colour bands into a resistance value, with tolerance, and for 6-band parts the temperature coefficient too. It also works in reverse: enter a resistance and it rounds to the nearest standard E-series value and shows the matching 4-band or 5-band colours. The colour assignments follow the international marking standard IEC 60062, the same code printed on through-hole resistors from every major manufacturer.
How to use it
- Choose the direction: colours to value, or value to colours.
- For colours to value, select the number of bands on your resistor (4, 5 or 6).
- Hold the resistor so the tolerance band is on the right. It is usually gold, silver or brown, often with a slightly wider gap before it.
- Enter the colours from left to right. The result shows resistance, tolerance and, for 6 bands, the temperature coefficient.
- For value to colours, type the resistance you need and pick 4 or 5 bands. The tool rounds to the nearest standard value and returns the bands to look for.
How the resistor colour code works
Each colour stands for a digit:
| Colour | Digit | Multiplier | Tolerance | Temp. coefficient |
|---|---|---|---|---|
| Black | 0 | ×1 | ||
| Brown | 1 | ×10 | ±1% | 100 ppm/K |
| Red | 2 | ×100 | ±2% | 50 ppm/K |
| Orange | 3 | ×1k | 15 ppm/K | |
| Yellow | 4 | ×10k | 25 ppm/K | |
| Green | 5 | ×100k | ±0.5% | |
| Blue | 6 | ×1M | ±0.25% | 10 ppm/K |
| Violet | 7 | ×10M | ±0.1% | 5 ppm/K |
| Grey | 8 | ×100M | ±0.05% | |
| White | 9 | ×1G | ||
| Gold | ×0.1 | ±5% | ||
| Silver | ×0.01 | ±10% |
4 bands: digit, digit, multiplier, tolerance. Yellow, violet, red, gold reads as 47 × 100 = 4,700 Ω, which is 4.7 kΩ at ±5%. So any real part with those bands should measure between 4,465 Ω and 4,935 Ω.
5 bands: three significant digits, then multiplier and tolerance. Precision resistors use this format. Brown, black, black, red, brown gives 100 × 100 = 10 kΩ at ±1%.
6 bands: the same as 5 bands, plus a final band for temperature coefficient in parts per million per kelvin. A 10 kΩ resistor rated at 100 ppm/K drifts by about 1 Ω for each degree of temperature change. A 50 K rise therefore adds roughly 50 Ω, or 0.5%.
Why values snap to the E-series
Resistors are not made in every possible value. They come in the preferred number series defined in IEC 60063. These series are named for how many values they place in each decade:
- E12 (10% parts): 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82
- E24: 5% and 2% parts
- E96: 1% parts
- E192: 0.5% and tighter
The steps are spaced roughly evenly on a logarithmic scale, so neighbouring values overlap their tolerance windows. That spacing is why a 4-band code with two significant digits suits the E12 and E24 values, while E96 values such as 10.2 or 48.7 need the third digit that a 5-band code provides. If you type 4,800 Ω, the tool returns the nearest standard value rather than a value you could not buy.
What it does not do
The tool decodes the colours you enter. It cannot tell which end of a physical resistor is band one, and it cannot correct for faded or discoloured paint. It does not decode the numeric codes printed on surface-mount resistors, and it says nothing about power rating, which you judge from the body size or the datasheet. When a reading matters, confirm it with a multimeter.
FAQ
Which end of a resistor do I start reading from?
Start from the end opposite the tolerance band. Gold and silver are never used as the first band, so if one end is gold or silver, that end goes on the right. On precision parts with a brown tolerance band, look for the wider gap before the last band.
Why does my multimeter reading not match the calculated value exactly?
Tolerance allows the part to sit anywhere inside its stated range. A 1 kΩ ±5% resistor can legitimately measure anywhere from 950 Ω to 1,050 Ω. Your meter’s own accuracy, test lead resistance and other components still connected in the circuit can also shift the reading.
What does the sixth band mean?
It gives the temperature coefficient, which is how much the resistance changes per degree of temperature. It is expressed in ppm/K, so lower numbers mean a more stable part. This matters in precision measurement, sensor and reference circuits, and rarely in everyday hobby builds.
Should I choose 4 or 5 bands in value-to-colours mode?
Choose based on the part you are buying or identifying. General-purpose carbon film resistors at 5% almost always use 4 bands. 1% metal film resistors, the common choice in modern kits, use 5 bands because their E96 values need three significant digits.