Resistor Color Code Calculator
Decode resistor color codes quickly and accurately. Select the colors of each band on your resistor to calculate its resistance value, tolerance, and acceptable range. Supports both 4-band (±5% to ±10% tolerance) and 5-band (±1% to ±0.1% tolerance) resistors. Essential for electronics hobbyists, students, and engineers.
What is the resistor color code and why is it used?
The resistor color code is a standardized system using colored bands to indicate a resistor's resistance value, tolerance, and sometimes temperature coefficient. Each color represents a specific number (Black=0, Brown=1, Red=2, Orange=3, Yellow=4, Green=5, Blue=6, Violet=7, Gray=8, White=9). This system was created because resistors are too small to print numbers on. It allows quick identification without specialized equipment. The standard was established by the Electronic Industries Alliance (EIA) and is used worldwide in electronics.
How do you read a 4-band resistor color code?
For 4-band resistors: Band 1 (first digit) and Band 2 (second digit) form a 2-digit number. Band 3 (multiplier) tells you how many zeros to add or the power of 10. Band 4 (tolerance) indicates accuracy. Example: Brown-Black-Red-Gold = 1, 0, ×100, ±5% = 10 × 100 = 1000Ω = 1kΩ ±5%. Read left to right - the tolerance band (gold/silver) is usually on the right and slightly separated. If unsure which end to start, gold/silver tolerance band is always last.
What is the difference between 4-band and 5-band resistors?
4-band resistors: 2 digits + multiplier + tolerance = 10% to 5% tolerance, common in general electronics. 5-band resistors: 3 digits + multiplier + tolerance = 1% to 0.1% tolerance, used in precision circuits. Example: 4-band (Brown-Black-Red-Gold) = 10 × 100 = 1kΩ ±5%; 5-band (Brown-Black-Black-Brown-Brown) = 100 × 10 = 1kΩ ±1%. The extra digit in 5-band provides finer resistance values (like 1.21kΩ instead of just 1.2kΩ). 6-band resistors add a temperature coefficient band.
What do tolerance colors mean and why does it matter?
Tolerance indicates how much the actual resistance can vary from the marked value. Gold = ±5% (most common), Silver = ±10%, Brown = ±1%, Red = ±2%, Green = ±0.5%, Blue = ±0.25%, Violet = ±0.1%. Example: A 1000Ω resistor with ±5% tolerance can be 950Ω to 1050Ω. Why it matters: Precision circuits (audio, measurement) need tight tolerance (±1% or better). General circuits can use ±5% or ±10%. Tighter tolerance costs more but ensures circuit accuracy. Always check tolerance when replacing resistors in sensitive equipment.