Amps to Watts Calculator
Convert current in amps to power in watts at any voltage — for example, to see how much load a 15 A or 20 A circuit can carry.
How to use the Amps to Watts Calculator
- Enter the current in amps.
- Enter the voltage.
- Choose DC or AC (single- or three-phase) and the power factor.
How it works
- DC: P = V × I
- AC single-phase: P = V × I × PF
- AC three-phase: P = √3 × V × I × PF
For household circuits with resistive loads, watts are simply volts × amps: 20 A × 120 V = 2,400 W. Because breakers should not carry more than 80% of their rating continuously, plan for 1,920 W on a 20 A, 120 V circuit.
Popular amps to watts conversions
- 1 amps to watts
- 2 amps to watts
- 3 amps to watts
- 4 amps to watts
- 5 amps to watts
- 6 amps to watts
- 7 amps to watts
- 8 amps to watts
- 9 amps to watts
- 10 amps to watts
- 11 amps to watts
- 12 amps to watts
- 13 amps to watts
- 14 amps to watts
- 15 amps to watts
- 16 amps to watts
- 17 amps to watts
- 18 amps to watts
- 19 amps to watts
- 20 amps to watts
- 21 amps to watts
- 25 amps to watts
- 30 amps to watts
- 35 amps to watts
- 40 amps to watts
- 45 amps to watts
- 50 amps to watts
- 0.5 amps to watts
- 1.5 amps to watts
- 2.5 amps to watts
Circuit capacity
| Breaker | Max at 120 V | Continuous (80%) | Max at 240 V |
|---|---|---|---|
| 15 A | 1,800 W | 1,440 W | 3,600 W |
| 20 A | 2,400 W | 1,920 W | 4,800 W |
| 30 A | 3,600 W | 2,880 W | 7,200 W |
| 40 A | 4,800 W | 3,840 W | 9,600 W |
| 50 A | 6,000 W | 4,800 W | 12,000 W |
Frequently asked questions
How many watts is 15 amps?
1,800 W at 120 V (1,440 W continuous).
How many watts is 20 amps at 240 V?
4,800 W.
How many watts is 10 amps?
1,200 W at 120 V or 2,400 W at 240 V.
Why use only 80% of a breaker?
Breakers and wiring heat up under sustained load; the NEC limits continuous loads (3 hours or more) to 80% of the rating.