Resistor Color Code Calculator
A 4-band resistor encodes its value in colored stripes: two significant digits, a power-of-ten multiplier, and a tolerance. Reading them by eye is easy to get wrong, especially with similar shades. Select the color of each band below and this calculator decodes the resistance in ohms (with kilohm and megohm conversions) and the tolerance percentage using the fixed IEC 60062 values. Every color maps to one unchanging number, so the result is exact arithmetic, not an estimate. Use it to verify a part before you solder it in.
Resistor color code formula
Resistance = (digit1 * 10 + digit2) * multiplier
Kilohms = resistance / 1,000
Tolerance ohms = resistance * tolerance% / 100
Low value = resistance - tolerance ohms
High value = resistance + tolerance ohms
The two digit bands form a two-figure number; the multiplier band scales it by a power of ten. The tolerance band gives the allowed percentage spread, which the calculator converts to an absolute range in ohms.
Color code reference
- Digit colors: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9.
- Multiplier: gold is times 0.1 and silver is times 0.01 for sub-ten-ohm values.
- Tolerance: brown 1 percent, red 2 percent, gold 5 percent, silver 10 percent.
- Bands are read from the end where they are grouped closest together.
- The scheme is defined by IEC 60062, the international marking-code standard.
Resistor color code: frequently asked questions
How does the resistor color code work?
On a 4-band resistor the first two bands are significant digits, the third band is a power-of-ten multiplier, and the fourth band is tolerance. The IEC 60062 standard assigns each color a fixed value: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9.
What does the multiplier band mean?
The third band multiplies the two-digit value by ten raised to that color's number. Black is times 1, brown times 10, red times 100, and so on. Gold is times 0.1 and silver is times 0.01, used for resistances below ten ohms.
What do the tolerance band colors mean?
The fourth band gives tolerance: brown is plus or minus 1 percent, red 2 percent, gold 5 percent, and silver 10 percent. A missing fourth band historically meant 20 percent. Gold and silver are the most common on general-purpose resistors.
How is the resistance value computed?
Resistance equals (first digit times ten, plus second digit) times the multiplier. For brown, black, red the digits are 1 and 0, giving 10, times the red multiplier of 100, equals 1,000 ohms, or 1 kilohm, with the tolerance read from the fourth band.
Why are color codes standardized?
Standardized colors let the same resistor be read anywhere in the world without printed text, which would be too small to read on tiny components. The scheme is defined in IEC 60062, the international standard for marking codes for resistors and capacitors.
Official sources
- International Electrotechnical Commission: IEC 60062 marking codes for resistors and capacitors.
- National Institute of Standards and Technology: SI prefixes (kilo, mega).
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.