Example 1: Red Violet Brown Gold
A resistor with bands Red, Violet, Brown, and Gold has:
Band 1 = 2, Band 2 = 7, Multiplier = x10
Resistance = 27 x 10 = 270 Ohm
Tolerance = +/-5 percent
Resistor Color Code (4-band)
Decode 4-band resistors using two significant digits, a multiplier, and a tolerance band.
Pick the resistor bands visually. The value updates instantly as you click each color.
Band 1
First digit
Band 2
Second digit
Band 3
Multiplier
Band 4
Tolerance
Introduction
The resistor color code calculator helps decode common 4-band resistors quickly and accurately. This is useful when you are assembling circuits, repairing electronics, checking component values from a kit, or identifying a resistor in a board without printed numeric markings. Many small resistors rely on color bands because text would be too small to read on the component body.
A standard 4-band resistor uses two significant digits, one multiplier band, and one tolerance band. With a quick decode, you can confirm whether a resistor is 220 Ohm, 4.7 kOhm, 100 kOhm, or another value before using it in a design. This page turns the color sequence into a readable resistance value and tolerance.
It is a handy reference when sorting components, verifying kit parts, or checking common resistor values during prototyping, repair, and basic circuit analysis.
Formula
Resistance = (Band1 x 10 + Band2) x Multiplier
The tolerance band gives the expected variation above or below the nominal resistance value.
Variable Definitions
Band 1 = first significant digit
Band 2 = second significant digit
Multiplier = decimal scale factor applied to the first two digits
Tolerance = allowed percentage variation from nominal value
Units
Resistor values are typically expressed in Ohm, kOhm, or MOhm. The calculator shows the raw resistance value in Ohm and includes the selected tolerance band so the acceptable value range can be understood during testing or troubleshooting.
Worked Examples
Example 2: Brown Black Orange Gold
A resistor with bands Brown, Black, Orange, and Gold gives:
Band 1 = 1, Band 2 = 0, Multiplier = x1000
Resistance = 10 x 1000 = 10000 Ohm, or 10 kOhm
Tolerance = +/-5 percent
Practical Notes
Always read the bands from the correct side of the resistor. The tolerance band is usually spaced slightly apart from the others, which helps indicate the reading direction. If the resistor is already installed in a circuit, the measured value with a multimeter may differ because of parallel circuit paths. For accurate verification, isolate one lead when needed.
Some 4-band resistors use gold or silver as multiplier bands for very low resistance values. Gold represents a multiplier of x0.1 and silver represents x0.01, so the calculator includes those options for low-ohm decoding.