How does the Circuit Breaker Sizing Calculator work?

Calculate circuit maximum current Then: Breaker must exceed running current for motor inrush Then: Typical breaker = current × 1.25 (non-motor) or × 2.5 (motor) Then: Match breaker to wire ampacity (wire must handle breaker rating).

Can you give an example of how to use the Circuit Breaker Sizing Calculator?

Example: Input 40A circuit, #8 wire gives a result of 50A breaker.

Is the Circuit Breaker Sizing Calculator free to use?

Yes — completely free with no registration, download, or subscription required. All calculations happen instantly in your browser.

How accurate is the Circuit Breaker Sizing Calculator?

Our Circuit Breaker Sizing Calculator uses verified mathematical formulas and is accurate to multiple decimal places. Results are calculated in real-time using the same methods used by professionals.

Specialized

Circuit Breaker Sizing Calculator

Wire Gauge (AWG)

Selects appropriate circuit breaker to protect circuits from overcurrent while allowing normal operation. Wrong sizing causes nuisance trips or fire risk.

Difficulty:intermediate

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Did You Know?

Improper breaker sizing causes 15-20% of electrical fires; proper selection prevents catastrophe.

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›Circuit Breaker Sizing

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Circuit Breaker Sizing Calculator

Circuit Breaker Sizing Calculator

What is Circuit Breaker Sizing Calculator?

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