MCPCalc

Circuit Breaker Size Calculator

Calculate the proper circuit breaker size based on load wattage, voltage, and load type with NEC-compliant continuous load adjustments and wire gauge recommendations.

Scratchpad (not saved)

What This Calculator Does

Calculate the proper circuit breaker size based on load wattage, voltage, and load type with NEC-compliant continuous load adjustments and wire gauge recommendations.

It combines Load (Watts), Voltage, Load Type, Safety Factor (%) to estimate Recommended Breaker Size, Recommended Wire Gauge, Actual Load Current.

Formula & Method

Load current is I=\frac{P}{V}. For continuous loads, adjusted current is I_a=I\cdot\frac{SafetyFactor}{100} (typically 125%). Recommended breaker is the next standard size at or above I_a.

Notation used in the formulas: R = Recommended Breaker Size; x_{1} = Load (Watts); x_{2} = Voltage; x_{3} = Load Type; x_{4} = Safety Factor (\%).

Method summary: inputs are normalized to consistent units, core equations are evaluated, then secondary values are derived and rounded for display.

Use this calculator for quick scenario analysis. Start with baseline values, change one driver at a time, and compare how sensitive the results are to each input shown above.

Inputs Used

  • Load (Watts): Used directly in the calculation.
  • Voltage: Used directly in the calculation.
  • Load Type: Used directly in the calculation.
  • Safety Factor (%): Used directly in the calculation.

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