Resistor Color Code Calculator

How to use

1. 1Pick Decode colors to read a physical resistor, or Build from value to synthesise the bands for a target ohm value.
2. 2In Decode mode, choose the band count (3, 4, 5, or 6) to match the resistor in front of you, then click each band to select its color. The visual resistor and the resistance readout update instantly.
3. 3Read the resistance, tolerance band, +/- range, and (for 6-band parts) the temperature coefficient. The closest E-series preferred value is shown so you can confirm the part matches a stocked component.
4. 4In Build mode, type a value using engineering shorthand: 4.7k, 470, 1M, 1k2 (1.2 kΩ), 4k7 (4.7 kΩ), 47R (47 Ω), 0.1, 22 kΩ all parse correctly. Pick the band count, tolerance color, and ppm color (for 6-band).
5. 5Use Copy bands or Copy result to paste the colors or the value into your notes, a BOM, or a chat with a teammate.

About this tool

Resistor Color Code Calculator reads and writes the colored band markings used on through-hole, axial-lead resistors. It supports the four common variants: the 3-band code (digit, digit, multiplier; 20% tolerance assumed), the 4-band code (the most common consumer code, with a tolerance band), the 5-band code (an extra significant figure for tighter parts), and the 6-band code (adds a temperature coefficient in ppm/°C, used on precision resistors). Decode mode is the everyday workflow: pick the colors you see on the resistor and the tool prints the resistance in human form (e.g. 4.7 kΩ), the raw ohm value, the tolerance band as a percentage, the +/- range so you can predict drift, the temperature coefficient when the part has six bands, and the closest preferred value from the IEC 60063 E-series (E6, E12, E24, E48, E96) so you know whether the resistor matches a standard stocked part. Build mode runs the lookup in reverse: type a target value with the engineering shorthand most data sheets use (4.7k, 1M, 470R, 1k2, 4k7, 0.1, 22 kΩ) and the calculator chooses significant figures, picks the matching multiplier color, and lays the bands out on a visual resistor along with your tolerance and ppm band selections. The visual resistor is rendered with SVG, so the body, leads, and bands stay sharp at any size, and the live render uses the exact colors the tool will report. A full color reference table at the bottom of the page shows what each color encodes for digits, multipliers, tolerance, and ppm. Useful for hobbyist electronics, robotics, hi-fi and audio circuits, repair and reflow work, EE coursework and labs, and any time you have a strip of resistors and need to read or order a specific value. Everything runs in your browser; no upload, no signup, no API calls.

Free to use. Works in your browser. No signup, no login.