fyrabandkod

Fyrabandkod is the Swedish term for the four-band color code used on many resistors to indicate their nominal resistance and tolerance. In this system, the first two bands encode the significant digits, the third band is the multiplier (the power of ten by which the digits are multiplied), and the fourth band specifies the tolerance.

The color-to-digit mapping used in the first two bands is: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9. The third band uses the same colors to indicate the multiplier as a power of ten (for example brown = x10, red = x100, green = x100000), while gold and silver denote multipliers of x0.1 and x0.01 respectively. The fourth band denotes tolerance, commonly brown 1%, red 2%, gold 5%, silver 10%, and no band indicating 20%.

Reading orientation is important: the tolerance band is usually separated slightly from the other three bands, and the digits are read beginning from the end closer to the digits. An example is red–violet–brown–gold, which yields a resistance of 27 × 10 = 270 ohms with a tolerance of ±5%.

Variants include the five-band color code, which uses three digits plus a multiplier and a tolerance, and occasionally a sixth band for temperature coefficient. Fyrabandkod is most common on older carbon film and some through-hole resistors; many modern surface-mount resistors use printed numeric markings instead. The system is standardized in many regions under IEC guidelines and remains a basic technique in electronics identification and repair.