Circuit Load Calculator

Verify the load on a breaker is within the 80 percent continuous-use limit.

Circuit Load
— amps
Versus breaker limit.

Usage Tip

Lights and receptacles on the same circuit share that limit, so total everything that runs at once.

THE MATH
amps = watts ÷ voltage
safe limit = breaker rating × 0.80
A breaker can carry only 80 percent of its rating on a continuous load. Amps are the load wattage divided by the voltage; comparing that to the limit shows if the circuit is overloaded.
Enter the total load in watts, the circuit voltage (120 or 240), and the breaker size.
Green means the load is within the continuous limit; red means it is over.
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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.