Resistor color bands

Colored bands on resistors indicate their ohmic value and tolerance, an internationally standardized code used in electronic components.

About this subject

Colored bands on resistors form an essential coding system to identify resistance value, tolerance, and sometimes temperature coefficient. This code, known as the resistor color code, follows IEC 60062 and has been widely used since the mid-20th century. Each color represents a digit from 0 to 9 (black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, gray=8, white=9). The first three bands indicate two significant digits and the multiplier (power of ten), while the fourth band denotes tolerance (gold=±5%, silver=±10%). Five-band or six-band versions add precision and thermal coefficient.

The resistor color code originated in the 1920s when the Radio Manufacturers Association (RMA) standardized the system to ease identification of carbon composition resistors. Previously, values were printed as numbers, which became hard to read on small components. Specific colors were chosen to avoid confusion under different lighting conditions; for example, brown and red are contrasting, while blue and violet can be confused, so violet was given a lighter hue. Military and aerospace resistors often use six-band variants that include temperature coefficient, crucial for thermally sensitive applications.

Reading colored bands is a fundamental skill for electronics professionals and hobbyists. While online calculators and scanning apps exist, manual reading remains relevant for maintenance and DIY projects. The reading always starts from the band closest to one end. Through-hole resistors use this system, whereas surface-mount resistors (SMD) employ numeric or alphanumeric codes. Maker culture often involves mnemonics like "Black Brown Red Orange Yellow Green Blue Violet Gray White" to remember the color sequence.

Frequently Asked Questions

How to read a 4-band resistor?

The first band is the first digit, the second band is the second digit, the third band is the multiplier (power of ten), and the fourth band is the tolerance. Example: brown, black, red, gold = 10 * 10² Ω = 1000 Ω with ±5% tolerance.

What is the difference between 4-band and 5-band resistors?

5-band resistors have three significant digits instead of two, allowing higher precision. The first three bands are digits, the fourth is the multiplier, and the fifth is the tolerance.

Why are gold and silver used for tolerance?

Gold represents ±5% tolerance and silver ±10%. These colors were chosen because they are easy to distinguish and are not used as digits (gold and silver are not in the 0-9 digit table).