Enter your load details — Input Type, Electrical Phase, Voltage, Power Factor, and Load Type — and the Breaker Size Calculator works out your Recommended Breaker Size along with the Calculated Load Current, Applied Safety Factor, and a list of Available Standard Sizes to choose from.
Recommended Breaker Size
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Calculated Load Current
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Applied Safety Factor
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Available Standard Sizes
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Calculate the load current, apply the appropriate safety factor (typically 125% for continuous loads), then select the next standard breaker size that meets or exceeds this value. Never downsize below the calculated requirement.
The 80% rule states that continuous loads should not exceed 80% of the breaker's rating. This calculator automatically applies a 125% safety factor (equivalent to the 80% rule) to ensure proper sizing for continuous loads.
Yes, select 'Three-Phase AC' and 'Motors' as the load type. The calculator will account for the three-phase power factor and apply appropriate safety factors for motor starting currents.
Common residential breaker sizes include 15A, 20A, 25A, 30A, 40A, 50A, 60A. Commercial and industrial applications use larger sizes like 70A, 80A, 100A, 125A, 150A, 200A and higher.
Common causes include loose connections, damaged wiring, actual load exceeding nameplate ratings, or a faulty breaker. Have a licensed electrician inspect the circuit to identify the root cause.
No, never replace a breaker with a higher rating without upgrading the wire size and ensuring the circuit can safely handle the increased current. The wire gauge must match or exceed the breaker rating.
No, this calculator provides estimates for planning purposes only. Always consult a licensed electrician for final sizing, code compliance, and installation. Local codes may have specific requirements not covered here.