Select the color bands on a resistor to read its resistance and tolerance — or find the colors for a known value.
Resistors use colored bands to encode their value because the components are too small for printed numbers. The standard four-band code uses two digits, a power-of-ten multiplier and a tolerance band. A brown-black-red-gold resistor reads 1-0-×100 = 1,000 Ω ±5%.
The sequence is always read from the band closest to one end of the body. The tolerance band (gold or silver) is usually spaced slightly further from the others, which tells you which end is which. Five-band and six-band codes add a third digit and sometimes a temperature coefficient, but four bands cover the majority of through-hole resistors.
The mnemonic devices for remembering the code are many and none are universally polite, so this tool replaces them: pick the colors you see, and the value appears.
Value = (band1 × 10 + band2) × multiplier. Tolerance: gold ±5%, silver ±10%, brown ±1%, red ±2%.
The tolerance band (gold or silver) is usually the last one and slightly separated. Start from the opposite end.
Five-band resistors add a third digit for precision. This tool currently covers the 4-band code, which is the most common in hobbyist electronics.
Black means 0, and a 0% tolerance would mean the value is exact — which no resistor is. The tightest standard tolerance is grey at ±0.05%, used in precision applications.
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