Convert 4-band resistor colors into resistance and tolerance.
How resistor color code is worked out
Resistors use colored bands to show their value. Pick the colors of each band and this calculator returns the resistance in ohms and the tolerance range.
It covers the common 4-band code used in most through-hole resistors.
Using the calculator
- Select the first two significant-digit bands.
- Select the multiplier band.
- Select the tolerance band and read the value.
Formula reference
resistance = (digit1 × 10 + digit2) × 10^multiplier
A worked example
Take the starting scenario, a band 1 of Brown, band 2 of Black, multiplier of Red. That gives a resistance of 1 kΩ. Underneath, Tolerance comes out at ±5% and Range at 950 Ω – 1.05 kΩ. Change any field and every figure updates as you type.
Questions people ask about this
How do resistor color codes work?
The first two bands are digits, the third is a power-of-ten multiplier, and the fourth is tolerance.
What do the tolerance colors mean?
Brown is ±1%, red ±2%, gold ±5% and silver ±10% — how much the real value may vary.
What about 5-band resistors?
Those add a third significant digit. This tool covers the common 4-band type.