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Resistor Color Code Calculator

Pick the four color bands to decode the resistor's resistance, tolerance, and value range.

How it is calculated

This tool reads a 4-band resistor. Bands 1 and 2 are digits (black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9). Band 3 is the multiplier, a power of ten (black ×1, brown ×10, red ×100, and so on up to blue ×1,000,000; gold ×0.1; silver ×0.01). Band 4 is the tolerance: brown ±1%, red ±2%, gold ±5%, silver ±10%.

The formula is R = (10 × band1 + band2) × 10^multiplier in ohms. The tool also shows the guaranteed range R × (1 ± tolerance / 100), and writes values in Ω, kΩ or MΩ. Hold the resistor so the tolerance band (gold or silver) is on the right. Five-band and six-band resistors are not covered.

Worked example

Bands: brown, black, orange, gold. Brown = 1 and black = 0, so the digits are 10. Orange as a multiplier is 10³ = 1,000. R = 10 × 1,000 = 10,000 Ω, shown as 10 kΩ. Gold means ±5%, so the real value lies between 10,000 × 0.95 and 10,000 × 1.05, which is 9.5 kΩ – 10.5 kΩ.

Try this example →

Common mistakes

  • Reading the bands from the wrong end. The tolerance band (gold or silver) goes on the right; starting from it reverses the digits.
  • Treating the third band as a third digit. On a 4-band resistor it is a multiplier, so orange means ×1,000, not 3.
  • Confusing gold and silver as multipliers with gold and silver as tolerances. The same colours mean ×0.1 and ×0.01 in band 3, but ±5% and ±10% in band 4.
  • Trusting the marked value for precision work. The actual resistance can be anywhere in the tolerance range, so measure it with a meter when it matters.

About this calculator

This calculator decodes a 4-band resistor color code using the standard EIA color chart: the first two bands give the significant digits, the third is the multiplier, and the fourth is the tolerance, combining to give the resistance in ohms (Ω), kilohms (kΩ) or megohms (MΩ).

Electronics hobbyists, technicians and students use it instead of memorizing the color chart or reaching for a multimeter, especially when sorting a mixed bin of resistors.

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Comments (1)

  • Editorial team

    This reads standard four-band resistors only: two digits, a multiplier and a tolerance. Five-band parts, which carry three digits, need a different reading, so count the bands before you start. Hold the resistor so that the tolerance band, usually gold or silver and set slightly apart, is on the right. A multimeter reading within the shown range means the part is fine, and a reading outside it points to a damaged part or misread colours. Which band count do you most often meet?

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