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Circuit Breaker Sizing Calculator

Find the correct circuit breaker rating for any electrical load by entering the full-load current and a safety factor. Use this during panel design, home wiring projects, or electrical code compliance checks.

Load Current (A)

Safety Factor

Fill in the required fields to see your result.

Electrical

Short Circuit Current Calculator

Compute the available short-circuit current (ASCC) at a fault point downstream of a transformer, accounting for transformer impedance and cable impedance to the fault location. Use this to verify that breakers and fuses have a sufficient interrupting rating.

Transformer Size (kVA)

Transformer Impedance (%)

System Voltage

Cable Length to Fault (ft)

Cable Size (AWG/kcmil)

Fill in the required fields to see your result.

Key differences

	Circuit Breaker Sizing Calculator	Short Circuit Current Calculator
Category	Electrical	Electrical
Inputs required	2	5
Result	Circuit Breaker Size (A)	Short Circuit Current (A)
What it does	Find the correct circuit breaker rating for any electrical load by entering the full-load current and a safety factor. Use this during panel design, home wiring projects, or electrical code compliance checks.	Compute the available short-circuit current (ASCC) at a fault point downstream of a transformer, accounting for transformer impedance and cable impedance to the fault location. Use this to verify that breakers and fuses have a sufficient interrupting rating.