Circuit Breaker Sizing Calculator

Circuit Breaker Sizing Calculator


  1. Enter the total load in watts (W) in the “Load (Watts)” field.
  2. Enter the voltage (V) of your circuit in the “Voltage (Volts)” field.
  3. Select a safety factor from the “Safety Factor” dropdown menu.
  4. Click the “Calculate” button to get the recommended circuit breaker size in amperes (A).

Formulas Used

The calculator uses the following formulas:

  • Load Current (A): Load Current (A) = Load (W) / Voltage (V)
  • Breaker Size (A): Breaker Size (A) = Load Current (A) x Safety Factor

What is a Safety Factor?

The safety factor is a multiplier applied to the calculated load current to ensure the circuit breaker can handle unexpected surges and variations in electrical demand. It helps prevent the breaker from tripping unnecessarily and accounts for potential overloading conditions, heat dissipation, and overall system reliability.

Typical safety factors include:

  • 1.25 (25%): Commonly used for general applications with no significant startup surges.
  • 1.50 (50%): Used where moderate surges or variations are expected.
  • 1.75 (75%): Applied in cases with higher potential for overload conditions.
  • 2.00 (100%): Used for very high surge loads or maximum safety.


If you encounter any issues or have further questions, please consult additional resources or seek expert advice.

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