Watts to Amps Calculator
Convert watts to amps (or amps to watts) for DC, single-phase, and three-phase AC circuits. Handles power factor and shows the 80% continuous-load limit for sizing breakers and wiring.
Use 1.0 for resistive loads (heaters), ~0.8–0.9 for motors and mixed loads.
Amps = Watts ÷ (Volts × PF)
16.67 A
13.33 A continuous limit (80% rule)
Circuit
AC single-phase
Power factor
0.9
Converting watts to amps
Watts measure power and amps measure current, so converting between them always needs the voltage. The base formula is amps = watts ÷ volts, but the exact form depends on the circuit. DC and purely resistive loads use it directly; single-phase AC divides by the power factor; and three-phase AC divides by √3 × volts × power factor. Getting the circuit type right matters most when you are sizing a breaker, choosing wire gauge, or checking whether an appliance will overload a receptacle.
Watts to amps at 120V (PF 1.0)
| Watts | Amps |
|---|---|
| 500 W | 4.17 A |
| 1,000 W | 8.33 A |
| 1,500 W | 12.5 A |
| 1,800 W | 15 A |
| 2,400 W | 20 A |
Watts to amps at 240V (PF 1.0)
| Watts | Amps |
|---|---|
| 1,000 W | 4.17 A |
| 2,400 W | 10 A |
| 3,600 W | 15 A |
| 4,800 W | 20 A |
| 7,200 W | 30 A |
Breaker size to maximum watts (amps to watts)
The most a circuit can carry at 100% and, for continuous loads, at the 80% code limit.
| Breaker | Max W @ 120V | Max W @ 240V | Continuous @ 120V (80%) |
|---|---|---|---|
| 15 A | 1,800 W | 3,600 W | 1,440 W |
| 20 A | 2,400 W | 4,800 W | 1,920 W |
| 30 A | 3,600 W | 7,200 W | 2,880 W |
| 40 A | 4,800 W | 9,600 W | 3,840 W |
| 50 A | 6,000 W | 12,000 W | 4,800 W |
Frequently asked questions
Divide watts by volts. For a DC or resistive circuit, amps = watts ÷ volts — so 1,800 watts at 120 volts is 15 amps. For AC circuits you also divide by the power factor, and for three-phase you divide by √3 × volts × power factor.
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