Resistor color bands

The colored bands on resistors form a universal code that indicates electrical value, tolerance, and reliability in electronic components.

About this subject

Resistors are passive components essential in electronic circuits, and their colored bands represent a globally standardized coding system. This code was introduced in the 1920s by the Radio Manufacturers Association (RMA), now the Electronics Industries Alliance (EIA), to enable quick identification of values without measurement. Each color corresponds to a digit from 0 to 9, following the rainbow sequence: black (0), brown (1), red (2), orange (3), yellow (4), green (5), blue (6), violet (7), gray (8), and white (9).

Reading a typical four-band resistor proceeds as follows: the first two bands represent the first two digits of the nominal value, the third band is the multiplier (power of 10), and the fourth band indicates tolerance. For example, a resistor with brown, black, red, and gold bands corresponds to 1 0 × 100 Ω = 1000 Ω (or 1 kΩ) with a tolerance of 5%. The gold band represents 5% tolerance, silver 10%, and the absence of a fourth band indicates 20%. Five-band versions exist for higher precision, with three significant digits.

This color code remains widely used today, despite the advent of surface-mount devices (SMDs). To aid memorization, students and technicians use mnemonics such as “Bad Boys Run Our Young Girls But Violet Generally Wins” (black, brown, red, orange, yellow, green, blue, violet, gray, white). Besides value, the colors are also standardized by IEC 60062, which defines coding for resistors and capacitors. The simplicity and visual effectiveness of this code have made it a lasting tool in electronics, enabling instantaneous component identification even in low-light conditions or cramped spaces.

Frequently Asked Questions

How to read resistor color bands?

The first two bands indicate the first two digits of the value, the third band is the multiplier (how many zeros to add), and the fourth band represents tolerance. For example, brown, black, red, gold = 1, 0, ×100, ±5% = 1000 ohms.

What tolerance does a gold band indicate?

A gold band indicates 5% tolerance. A silver band represents 10%, and the absence of a fourth band means 20% tolerance.

Why are colors used instead of numbers?

Colors are easier to read quickly on small components, allow identification even in low light, and are durable as they do not fade like numeric ink. The standard was established in the 1920s and remains in use globally.