Watts to Amps Calculator

Find how many amps an appliance or circuit draws from its wattage and voltage. Works for DC, single-phase AC (household) and three-phase AC.

How to use the Watts to Amps Calculator

Enter the power in watts.
Enter the voltage (120 V for standard US outlets, 240 V for large appliances).
Choose the circuit type and, for AC motors, the power factor.

How it works

DC: I = P ÷ V
AC single-phase: I = P ÷ (V × PF)
AC three-phase: I = P ÷ (√3 × V × PF)

The power factor (PF) is 1 for resistive loads like heaters and incandescent bulbs, and lower (about 0.8–0.95) for motors and many electronics. A 1,500 W heater on 120 V draws 1,500 ÷ 120 = 12.5 A. Electrical codes generally limit continuous loads to 80% of the breaker rating.

Watts to amps at 120 V and 240 V

Watts	Amps at 120 V	Amps at 240 V
100	0.83	0.42
500	4.17	2.08
1,000	8.33	4.17
1,200	10	5
1,500	12.5	6.25
1,800	15	7.5
2,000	16.67	8.33
2,400	20	10
3,000	25	12.5
3,600	30	15
5,000	41.67	20.83

Frequently asked questions

How many amps is 1500 watts?

12.5 A at 120 V, or 6.25 A at 240 V.

How many watts can a 15 amp circuit handle?

1,800 W maximum at 120 V, or 1,440 W for a continuous load (80%).

How many amps does a 2000 watt heater use?

About 16.7 A at 120 V — too much for a 15 A circuit.

What is power factor?

The ratio of real power to apparent power in an AC circuit. It is 1 for resistive loads and lower for motors.