Resistor Color Code

Digits, multiplier, tolerance, in that order

Reading a resistor always follows the same logic: first the significant digits (2 bands on 4-band resistors, 3 bands on 5- and 6-band resistors), then a multiplier band that applies a power of ten to the number formed by the digits, and finally the tolerance. For example, brown-black-red forms the number 10, and red as the multiplier applies ×100, giving 1,000 Ω (1 kΩ). Reading direction matters: the tolerance band (usually gold or silver, or set apart with a wider gap from the rest) always comes last, so it tells you which end to start from.

Gold and silver never represent a digit, they only ever appear as a multiplier (×0.1 and ×0.01, for resistors below 10 Ω) or as tolerance (±5% and ±10%). Orange, yellow and white, meanwhile, have no commonly used tolerance value: in practice only brown, red, green, blue, violet, grey, gold and silver show up in the tolerance band, alongside the absence of a fourth band entirely, which implies ±20%.

• 4-band: 2 digits + multiplier + tolerance.
• 5- and 6-band: 3 digits + multiplier + tolerance (+ temperature coefficient on the 6-band).
• Gold (×0.1) and silver (×0.01) only ever appear as multiplier or tolerance.
• No tolerance band at all: the historical default is ±20%.

From color code to ohm value

A 4-band yellow-violet-orange-gold resistor reads as follows: yellow (4) and violet (7) form 47; orange applies the ×1,000 multiplier; the result is 47,000 Ω, or 47 kΩ, with ±5% tolerance (gold), one of the most common values found in electronics kits.

A 6-band brown-black-black-red-brown-brown resistor has 3 digits (100), a red ×100 multiplier, reaching 10,000 Ω (10 kΩ) with ±1% tolerance (brown) and a 100 ppm/K temperature coefficient (also brown), meaning the resistance drifts by up to 100 parts per million of the nominal value for every degree Celsius of temperature change.

Through-hole, SMD, and why a visual code exists at all

The color code exists because through-hole resistors are usually too small to print legible numbers on every side of the cylindrical body; a colored ring, on the other hand, is visible from any angle. That's why it's still taught and used decades after alternatives became available: in prototyping, electronics kits, board repair and basic electronics education, a quick visual read still beats reaching for a magnifying glass.

Surface-mount resistors (SMD/SMT) generally don't use colored bands at all, they carry a numeric code printed directly on the flat top of the component, since their flat surface allows for it. The banded color code is therefore essentially a convention of the traditional through-hole resistor.