Watts to Amps Converter
Convert watts to amps for electrical circuit sizing, breaker selection, and appliance installation. Calculate current draw from power and voltage for 120V, 240V, and other circuits.
Formula & Reference
| Variable | Formula | Units |
|---|---|---|
| Watts to Amps Converter | Amps = Watts / Volts | amperes (A) |
Step-by-Step Examples
1,200 W at 120V.
- A = 1,200 / 120 = 10 A
- Microwaves typically on a dedicated 20A circuit
5,400 W at 240V.
- A = 5,400 / 240 = 22.5 A
- Electric dryers need 30A circuit (125% of 22.5 = 28.1 A)
7,200 W Level 2 at 240V.
- A = 7,200 / 240 = 30 A
- Level 2 EV charger typically requires a 40A dedicated circuit (NEC 125% rule)
Real-World Applications
Common Mistakes to Avoid
The NEC requires continuous loads (running over 3 hours) to not exceed 80% of circuit capacity. A 20A circuit should only carry 16A continuous load. Always size breakers at 125% of calculated amps.
Residential power is single-phase. Commercial 3-phase uses Amps = Watts / (Volts x 1.732). Using single-phase formula for 3-phase circuits is a significant error.
For AC circuits with motors and inductive loads, actual amps = W / (V x PF) where PF is power factor (often 0.85-0.95). For resistive loads (heaters, incandescent lights), PF = 1.0.