Electrical
Electrical Breaker Size Calculator
The breaker size for a load, including the 125% uplift a continuous load requires.
Result
A planning estimate, not a code calculation. Conductor sizing, overcurrent protection and load calculations are governed by the NEC as adopted and amended where you are, and by the listing of the equipment involved. Have the design confirmed by a licensed electrician and inspected. The breaker protects the conductor, so the wire must be sized for the breaker and not merely for the load. Motors, air conditioners and welders have their own sizing rules that override this.
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About this calculator
Can I fit a bigger breaker to stop nuisance tripping?
No. The breaker protects the wire. Fitting a larger one on the same conductor removes that protection and is a fire risk, not a fix. A breaker that trips repeatedly is reporting a real problem.
Why 125% for continuous loads?
Breakers and terminations heat up over time, and standard devices are not rated to carry their full nameplate current indefinitely. The 25% margin is what keeps them within their thermal rating.
Do motors follow this?
No. Motor circuits size the conductor on the full-load current table and the protection separately, often much higher, to allow starting current. This calculator does not cover them.
The formula
design amps = load x 1.25 if continuous; breaker = next standard size at or above that
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