Watts, Volts & Amps Calculator (DC, AC, 3-Phase)
Convert between watts, amps and volts for DC, single-phase AC and three-phase circuits, including power factor.
How to use
- 1Choose DC, single-phase or three-phase.
- 2Enter two of watts, volts and amps (and the power factor for AC motors).
How it's calculated
DC: P = V × I. Single-phase AC: P = V × I × PF. Three-phase: P = √3 × V(line-to-line) × I × PF.
Frequently asked questions
How many amps is a 1,500 W heater on 120 V?
1,500 ÷ 120 = 12.5 A — too much for a 15 A circuit shared with other loads.
What is power factor?
The ratio of real power to apparent power. Resistive loads (heaters) are 1.0; motors are often 0.8–0.9.
What's the difference between kW and kVA?
kW is real power; kVA is apparent power (V × I). kW = kVA × power factor.