Watts / Volts / Amps Calculator
Convert and calculate electrical values easily.
Watts / Volts / Amps Calculator
Enter any two of watts, volts and amps and the calculator solves the third using P = V × I. Use the power factor field for AC loads that are not purely resistive.
Fill any two fields and leave the third empty.
The relationship
Power (W) = Voltage (V) × Current (A). For AC circuits with motors or electronics, real power is lower than V × A by the power factor: W = V × A × PF.
Typical uses
- Checking whether a 1,500 W heater fits on a 15 A, 120 V circuit (it draws 12.5 A, leaving little margin).
- Sizing a fuse or cable for a 12 V DC load.
- Converting an appliance label’s amps into watts for the electricity cost calculator.
Measuring instead of calculating
A clamp meter reads current without breaking the circuit; a plug-in power meter reads watts directly and accounts for power factor. Both are covered in the electrical testing guides.
Working on live circuits can cause shock, arc flash and fire. Use a meter with the correct CAT rating and, where required, a qualified electrician.