Resistor Color Code Calculator
Decode resistor color bands to find resistance value, tolerance, and min/max range. Supports 4-band and 5-band resistors with a visual graphic. Enter colors or a value — free and private.
Color Code Reference Table
How Resistor Color Codes Work
Resistors use colored bands to indicate their resistance value, tolerance, and sometimes temperature coefficient. The system was standardized by the Electronic Industries Alliance (EIA) and is used on through-hole axial resistors worldwide. A 4-band resistor has two significant digit bands, one multiplier band, and one tolerance band. A 5-band resistor adds a third significant digit for higher precision. Reading left to right, you decode each band color into its numeric value, multiply by the multiplier, and apply the tolerance percentage to determine the acceptable range.
4-Band vs 5-Band Resistor Coding
A 4-band resistor encodes two significant digits (bands 1-2), a multiplier (band 3), and tolerance (band 4). For example, Red-Violet-Orange-Gold reads as 27 × 1,000 = 27kΩ ±5%. A 5-band resistor offers greater precision with three significant digits (bands 1-3), a multiplier (band 4), and tolerance (band 5). For example, Brown-Black-Black-Red-Brown reads as 100 × 100 = 10kΩ ±1%. The 5-band format is standard for precision resistors with 1% or tighter tolerances.
Reading Resistor Bands Correctly
Always start reading from the band closest to the lead end. The tolerance band (gold, silver, or a tight-tolerance color) is usually spaced slightly farther from the other bands. If the first band is gold or silver, flip the resistor — those colors never appear as the first significant digit. Common mistakes include reading the bands backwards or confusing similar colors like brown and red. This calculator eliminates guesswork by letting you select colors and instantly see the decoded value with min/max tolerance range.
Resistor Tolerance Explained
Tolerance indicates how much a resistor's actual value can deviate from its stated value. Gold (±5%) is the most common for general-purpose resistors. A 1kΩ ±5% resistor can measure anywhere from 950Ω to 1,050Ω. Precision applications use 1% (brown) or tighter tolerances. The tolerance band is always the last band on the resistor. When designing circuits, always account for the worst-case tolerance to ensure reliable operation across the full range of possible resistance values.