Circuit Breaker Calculator

Calculate the required breaker amperage and wire gauge for your electrical load with NEC compliance checking.

Total Load

Voltage

Safety Factor

Tab to move between fields

Breaker Size

20 A

Wire Gauge (AWG)12

Actual Current Draw15 A

Required Amps (w/ safety)18.75 A

Load Percentage75%

NEC 80% Rule1

How to Use This Calculator

Enter the Total Load in Watts for all devices on the circuit.
Select System Voltage (120V or 240V).
Set the Safety Factor (typically 1.25 per NEC 80% rule).
Review Recommended Breaker Size (amps) and Recommended Wire Gauge (AWG).
Select the next standard breaker size up (15, 20, 30, 40 amp) from the recommendation.

How the result changes with Total Load

Total Load: Total wattage of all devices on the circuit.
Voltage: Circuit voltage (120V standard, 240V for heavy appliances).
Safety Factor: NEC requires 125% for continuous loads. Use 100% for non-continuous loads.

Identify Input Parameters
Total Load = 1800, Voltage = 120, Safety Factor = 125 = 3 input(s) provided
Calculate Breaker Size
Breaker Size
20 = 20
Calculate Wire Gauge
Wire Gauge
12 = 12
Calculate Actual Current Draw
Actual Current Draw
15 = 15