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Resistor Calculator
Decode resistor color codes for 4-band and 5-band resistors. Find resistance value from color bands or get colors for a target resistance.
Enter any 2 of the 4 values — the rest will be calculated automatically.
Volts
Amps
Ohms Ω
Watts
Voltage
12 V
Current
2 A
Resistance
6 Ω
Power
24 W
Ohm's Law: V = I × R | P = V × I | P = I² × R | P = V² / R
How to Use the Resistor Calculator
Enter your values above for an instant result. This tool uses verified formulas and is optimised for users in USA, Canada, UK, Australia. All calculations happen in your browser — your data is never sent to our servers.
Frequently Asked Questions
How do you read resistor color codes?
For a 4-band resistor: bands 1&2 are digits, band 3 is multiplier, band 4 is tolerance. Red-Red-Red-Gold = 2,200Ω ±5%.