Amps to Watts Calculator
Convert amps to watts at any voltage and power factor.
This conversion is for load estimation only. Circuit and equipment sizing must follow the NEC and be verified by a licensed electrician.
How this calculator works
watts = volts × amps × power factor
For three-phase, multiply by 1.732 as well. Power factor is the gap between real power in watts and apparent power in volt-amps — generators and UPS units are rated in VA for exactly this reason.
Worked example
With current 15 , voltage 120 , power factor 1 , this calculator returns 1800 .
Frequently asked questions
How many watts is 15 amps?
At 120 V with a resistive load, 1,800 watts. At 240 V the same 15 amps delivers 3,600 watts, which is why heavy appliances run on the higher voltage.
What is power factor?
The ratio of real power to apparent power. Resistive loads like heaters and incandescent lamps have a power factor of 1. Motors and transformers run 0.8 to 0.9 because current lags voltage.
What is the difference between watts and VA?
Watts is the power actually doing work; VA is the product of voltage and current regardless of phase. They are equal only at unity power factor. Generators and UPS units are rated in VA because that is what the wiring carries.
How do I convert for three-phase?
Multiply by 1.732, the square root of three. Three-phase watts equals volts times amps times power factor times 1.732, using line-to-line voltage.