Using the calculator
Type the colours from left to right, like brown black red gold, and the calculator gives the resistance and tolerance, draws the resistor, and shows the working. Short names work too: bn bk rd gd. Swap to go the other way: type a value like 4.7k, 4k7 or 220, choose 4, 5 or 6 bands and a tolerance, and it gives the colours.
If the calculator says a band can't be a digit, the resistor is probably being read from the wrong end. Turn it round so the gold or silver band is on the right.
Resistor color code chart
| Colour | Digit | Multiplier | Tolerance | Temp. coefficient |
|---|---|---|---|---|
| Black | 0 | × 1 | – | 250 ppm/K |
| Brown | 1 | × 10 | ±1% | 100 ppm/K |
| Red | 2 | × 100 | ±2% | 50 ppm/K |
| Orange | 3 | × 1,000 | ±0.05% | 15 ppm/K |
| Yellow | 4 | × 10,000 | ±0.02% | 25 ppm/K |
| Green | 5 | × 100,000 | ±0.5% | 20 ppm/K |
| Blue | 6 | × 1,000,000 | ±0.25% | 10 ppm/K |
| Violet | 7 | × 10,000,000 | ±0.1% | 5 ppm/K |
| Grey | 8 | × 100,000,000 | ±0.01% | 1 ppm/K |
| White | 9 | × 1,000,000,000 | – | – |
| Gold | – | × 0.1 | ±5% | – |
| Silver | – | × 0.01 | ±10% | – |
| No band | – | – | ±20% | – |
Resistor color code chartstringmash.com/resistor-color-code
How to read the bands
On a 4-band resistor, the first two bands are digits, the third is a multiplier, and the fourth is the tolerance. Brown black red gold is 1 and 0, times 100, so 1,000 Ω, or 1 kΩ, within 5%.
A 5-band resistor has three digit bands before the multiplier, for more precise values: brown black black brown brown is 100 × 10 = 1 kΩ, within 1%. A 6-band resistor adds a sixth band for the temperature coefficient, how far the resistance drifts as it warms up, in parts per million per degree.
Which end is which
The tolerance band is usually set a little apart from the others, and gold and silver only ever appear as a multiplier or tolerance, never as the first band. So if one end has a gold or silver band, read from the other end.
The table follows the 2016 edition of the standard, IEC 60062. Some older charts give different tolerances for orange, yellow and grey.
Questions
What is brown black red gold?
1 kΩ, plus or minus 5%: brown 1, black 0, red times 100, gold 5%.
What colour is a 10k resistor?
Brown black orange, followed by the tolerance band: brown 1, black 0, orange times 1,000. Gold for 5%.
What does 4k7 mean?
4.7 kΩ. Writing the unit letter where the decimal point goes is a common way to print values, since a dot is easy to lose. The calculator reads it.