Result will appear here
If you know a circuit’s current rating (amps) and voltage, this calculator gives you the power in watts — useful for sizing generators, inverters, or checking a breaker’s total capacity.
How to Use This Calculator
Enter the current in amps and the voltage, then click Calculate to get the power in watts.
Formula
Watts = Amps × Volts.
For breaker and circuit sizing, always follow local electrical code and consult a licensed electrician.
Frequently Asked Questions
How many watts is a 15 amp, 120V circuit?
15A × 120V = 1800 watts is the theoretical maximum; in practice, circuits are typically loaded to no more than 80% of this for continuous use.
Why 80% and not 100%?
Electrical code generally limits continuous loads to 80% of a breaker’s rating for safety — check local code for exact requirements.
Does this work for 240V circuits too?
Yes — just enter 240 as the voltage instead of 120.