Calculate watts from volts and amps, amps and ohms, or volts and ohms. This watts calculator estimates electrical power, milliwatts, kilowatts, watt-hours, kilowatt-hours, voltage, current, and resistance.
Volts and amps:
Enter voltage and current. The calculator uses W = V × A.
Amps and ohms:
Enter current and resistance. The calculator uses W = A² × Ω.
Volts and ohms:
Enter voltage and resistance. The calculator uses W = V² ÷ Ω.
A watts calculator helps estimate electrical power when you know volts, amps, or ohms.
It can help with appliance loads, electronics projects, battery planning, solar estimates, power supply sizing, circuit loads, energy estimates, and basic electrical troubleshooting.
Your result shows estimated watts, milliwatts, kilowatts, watt-hours, kilowatt-hours, monthly energy estimate, voltage, current, resistance, formula used, wattage category, and comparison scenarios.
Use W = V × A when you know volts and amps. Multiply volts by amps to get watts.
Use W = A² × Ω. Square the amps, then multiply by ohms.
Use W = V² ÷ Ω. Square the volts, then divide by ohms.
No. Watts measure power. Watt-hours measure energy used over a period of time.