What This Calculator Is For
Use this calculator when you need to read a resistor from its color bands and quickly confirm the resistance and tolerance. It is useful for electronics labs, troubleshooting, resistor selection, and checking parts before installation.
Select Bands
How the Bands Work
A 4-band resistor uses two significant digits, a multiplier, and tolerance. A 5-band resistor uses three significant digits, a multiplier, and tolerance.
Resistance = significant digits × multiplier
Examples
Example 1
Brown, black, red, gold
10 × 100 = 1 kΩ ±5%
Range = 950 Ω to 1.05 kΩ
Example 2
Red, violet, orange, gold
27 × 1000 = 27 kΩ ±5%
Range = 25.65 kΩ to 28.35 kΩ
Example 3
Brown, black, black, red, brown
100 × 100 = 10 kΩ ±1%
Range = 9.9 kΩ to 10.1 kΩ
Reading Direction
The tolerance band is usually separated from the other bands and is commonly gold, silver, brown, red, green, blue, violet, or gray. Hold that band to the right before reading.
Some precision, fusible, military, and temperature-coefficient markings use additional conventions outside this calculator.
Measure unknown resistors with power removed and at least one lead isolated when connected circuit paths could affect the reading.