Resistor Color Code Calculator (Color to Value & Value to Color)

Calculate resistance and tolerance from a resistor's color code (4-band or 5-band). You can also enter a resistance value to find the matching band colors.

Tips

  • When holding a real resistor, orient it so the tolerance band (usually gold or silver) is on the right and read from the left. The band with the widest gap before it is the tolerance band.
  • The difference between 4-band and 5-band codes is the number of significant digits. Common carbon-film resistors use 4 bands, while precision metal-film resistors use 5 bands and often have tolerances of ±1% or tighter.
  • If the "Value to Color" mode can't find matching colors, the value may not fall on the standard E12/E24 series, or the tolerance you entered isn't one of the standard percentages (±1/2/5/10/20% etc.).
  • Gold and silver are used both as multiplier colors (×0.1 and ×0.01) and tolerance colors (±5% and ±10%), so the same color means something different depending on its position.
  • If the bands are hard to read in dim light or on a faded resistor, measure the resistance with a multimeter and enter that value into "Value to Color" mode to cross-check the expected color sequence.

Frequently Asked Questions

Resistors are tiny components, and printed numbers become hard to read once the part is mounted, oriented differently, or dirty with age. Colored bands remain legible even on small parts from a distance, which is why the Radio Manufacturers Association (RMA, now the EIA) standardized the color code system in the 1920s.

5-band resistors are generally more precise. A 4-band code can only express two significant digits, while a 5-band code expresses three, which is why precision metal-film resistors with tolerances of ±1% or tighter typically use 5 bands.

By convention, a missing tolerance band means ±20%. This is mostly seen on older or very inexpensive general-purpose resistors; most parts sold today include an explicit gold, silver, or brown tolerance band instead of leaving it blank.

Lighting color temperature and gradual discoloration of the resistor surface can make bands hard to distinguish. If possible, measure the resistance with a multimeter and use the "Value to Color" mode to work backward from the measured value.
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Side Note — The Color Code Follows the Order of the Rainbow

The resistor color code traces back to a standard set by the Radio Manufacturers Association (RMA, now the EIA) in the United States in the 1920s. During the vacuum-tube radio era, resistors were shrinking too small to print numbers on, so colored paint bands were adopted instead. The sequence from black (0) to white (9) roughly follows the wavelength order of visible light, from low-energy red tones to high-energy violet and white, which is widely believed to have made the scheme easier for engineers of the time to memorize.

A static table of resistor colors is easy to find with a quick search, but actually picking the colors you see on a real resistor to look up its value — or working backward from a desired resistance to the colors that represent it — is something a plain table can't do on its own. Sites like dCode and Digi-Key are well known as go-to conversion tools in the electronics hobbyist world, making the "color code calculator" one of the most classic tool categories in the space. Alongside the Ohm's law calculator in the same physics category, this tool rounds out the basic circuit-design calculations on the site.

Commercial resistors aren't sold at arbitrary values; they follow standardized series such as E12 (12 logarithmically spaced values like 10, 12, 15, 18, 22... multiplied by powers of ten) or the finer E24 series. The "Value to Color" mode in this tool simply rounds your input to the required number of significant digits and works backward from there, so entering a value outside the E12/E24 series may produce a color combination that doesn't correspond to any resistor actually sold.

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