Breaker Size Calculator
Estimate electrical load current and a preliminary circuit breaker size from load, voltage, and circuit type.
Results
Preliminary estimate based on the selected inputs.
This is a preliminary estimate only. Verify conductor ampacity, breaker type, load characteristics, applicable rules, and local electrical code before installation.
How to use the calculator
- Select AC or DC and the phase type where applicable.
- Choose whether to enter load power or load current.
- Enter voltage, power factor for AC, and a design margin.
- Review the automatically updated current estimate and preliminary breaker size.
Assumptions and limitations
This tool uses simplified electrical calculations. For AC, load current is estimated from real power, voltage, phase, and power factor. The standard-size result is a planning estimate only; it does not verify conductor ampacity, short-circuit ratings, interrupting capacity, motor starting requirements, or code compliance. Continuous-load requirements and other load-specific rules vary by jurisdiction and application. Consult a qualified electrician for actual installations.
