Resistor Color Code Calculator
Decode 4-band resistor color codes to find resistance values, or enter a resistance value to find matching color bands. Includes tolerance range and visual band display.
About the Resistor Color Code Calculator
Resistor color codes were standardized because printed numbers would be too small to read reliably on tiny components. The 4-band system uses two digit bands, one multiplier band, and one tolerance band. The value formula is (Band1 × 10 + Band2) × Multiplier. For example, Brown-Black-Red-Gold decodes as (1×10 + 0) × 100 = 1,000Ω = 1kΩ ±5%. Once you know the resistance value, use our Ohm's Law Calculator to find the resulting current or power dissipation in your circuit.
The E12 series (12 values per decade) is the most common set of standard resistor values. When you need a specific resistance that isn't a standard value, you can combine resistors in series (add values) or parallel (1/R_total = 1/R1 + 1/R2). For wiring electrical circuits, check our Voltage Drop Calculator to ensure your wiring is properly sized.
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For a related calculation, use Horsepower Calculator to convert between horsepower, kilowatts, torque, and RPM. Supports three calculation modes. Alternatively, use Ohm's Law Calculator to solve for voltage, current, resistance, or power (V, I, R, P) given any two known electrical values.