Work out resistor colour code instantly with clear inputs, formula shown and shareable results.
A four-band resistor encodes two significant digits, a power-of-ten multiplier and a tolerance. Brown-black-red-gold is 1, 0, times 100, so 1 kΩ at 5%. The tolerance band matters as much as the value: a 5% 1 kΩ part is guaranteed only to lie between 950 and 1050 ohms.
Colour code
R = (digit1 x 10 + digit2) x 10^multiplier, with the tolerance band giving the guaranteed spread
Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.
Start at the band nearest an end and furthest from the tolerance band. Gold and silver are almost always tolerance, so read away from them.
Precision parts use three significant digits plus multiplier and tolerance, so brown-black-black-brown-brown is 100 x 10 = 1 kΩ at 1%.