P = V × I
Electrical power equals voltage times current. Choose what to solve for and enter the other two values: find the power of a device, the current it draws (useful for choosing fuses, MCBs and wire sizes), or the voltage.
The result also shows kilowatts and horsepower, the energy used in an hour, and an example monthly use in kWh — the “units” on your electricity bill.
How to calculate electrical power
- 1
Choose what to solve for
Power, voltage or current.
- 2
Enter the other two
With their units.
- 3
Read power and energy use
W, kW, hp and kWh.
Key features
Solve any variable
P, V or I.
Energy estimate
kWh per hour and per month.
Many units
W, kW, mW, hp, kV, mA.
Load resistance
Shown for reference.
Common uses
- Home appliances: Estimate electricity units used.
- Wiring: Current draw for fuse and cable sizing.
- Solar and inverters: Size a backup system.
Tips and good to know
- US household outlets supply about 120 V, so a 1,500 W space heater draws about 12.5 A — close to the limit of a 15 A circuit.
- Units used = kW × hours. Multiply by your tariff to estimate the bill.
Frequently asked questions
How do I calculate watts from volts and amps?
Multiply them: 230 V × 6.5 A ≈ 1,495 W.
How many amps does a 2,000 W appliance draw at 230 V?
About 8.7 A (2,000 ÷ 230).
What is a unit of electricity?
One kilowatt-hour (kWh): using 1,000 W for one hour.