Home & DIY Calculators
Circuit Breaker Load Calculator
Enter your total connected wattage, voltage, and breaker rating to check your load against the National Electrical Code's 80% continuous-load guideline.
15.0 A
75% of breaker rating · 80% continuous-load limit is 16.0 A
Within the 80% continuous-load guideline.
The National Electrical Code recommends keeping continuous loads (running 3+ hours) at or below 80% of a breaker's rating. This is a planning estimate, not a substitute for a licensed electrician.
How to use this tool
- 1Add up the wattage of everything on the circuit.
- 2Enter your circuit voltage (commonly 120V or 240V).
- 3Enter the breaker's amp rating.
- 4See your load in amps and whether it's within the safe continuous-load limit.
Frequently asked questions
Why 80% and not 100%?+
The National Electrical Code requires continuous loads (running 3+ hours) to not exceed 80% of a breaker's rating, since breakers are rated for their full capacity only on shorter, intermittent loads.