Understanding Color Codes
Resistor color codes are a standardized system for marking the resistance value and tolerance of through-hole resistors using colored bands. This system was developed because the component body is too small for printed numbers to be reliably readable. The color bands are read from left to right, starting from the band closest to one end of the resistor.
A 4-band resistor has two significant digits, a multiplier, and a tolerance band. 5-band resistors add a third significant digit for higher precision. The color coding system follows a logical sequence: Black=0, Brown=1, Red=2, Orange=3, Yellow=4, Green=5, Blue=6, Violet=7, Gray=8, White=9. A common mnemonic is "BB ROY of Great Britain has a Very Good Wife."
How to Read Bands
Color Code Chart
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | x1 | - |
| Brown | 1 | x10 | 1% |
| Red | 2 | x100 | 2% |
| Orange | 3 | x1k | - |
| Yellow | 4 | x10k | - |
| Green | 5 | x100k | 0.5% |
| Blue | 6 | x1M | 0.25% |
| Gold | - | x0.1 | 5% |
| Silver | - | x0.01 | 10% |
E-Series
- E12 (10% tolerance): 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82.
- E24 (5% tolerance): 24 values per decade, includes all E12 values plus intermediates.
- E96 (1% tolerance): 96 values per decade for precision applications.
Frequently Asked Questions
Which end do I start reading from?
Start from the end where the bands are closer together. The tolerance band (gold or silver) is usually slightly separated from the other bands and is on the right side. If unsure, the first band will not be gold, silver, or black.
Why are some resistors 4-band and others 5-band?
4-band resistors provide two significant figures and are standard for 5% and 10% tolerance parts. 5-band resistors provide three significant figures for 1% and 2% precision resistors where the third digit adds necessary resolution.
Do SMD resistors use color codes?
No. Surface-mount resistors use a numerical marking system. A 3-digit code like "472" means 47 x 10^2 = 4700 ohms. Some very small SMD resistors have no markings at all and must be measured.