Circuit Breaker Calculator

Calculate load current, select a practical breaker, and estimate conductor size using 2024 Canadian Electrical Code ampacity values.

Phase

Calculate

VoltagePower factor

Load power

Continuous loadApply 125% sizing factor

Conductor details

MaterialAmpacity columnAmbient temperatureCurrent-carrying conductorsOne-way circuit length

Maximum voltage drop

Results

Calculated load current50 A

Suggested Standard Breaker50 A

Recommended Conductor8 AWGCopper · corrected ampacity 50 A

Minimum sizing current: 50 A
Ampacity-only minimum: 8 AWG
Estimated voltage drop: 5.12 V · 2.13%
Correction factors: 1 temp. · 1 grouping

12,000 W ÷ 240 V = 50 A

Sizing method

Load, protection, and conductor sizing are separate checks.

Calculate load

Uses voltage, phase, power, current, and power factor. Three-phase calculations use line-to-line voltage.

Size protection

Applies the selected continuous-load factor and moves to a common breaker rating.

Check conductor

Checks corrected ampacity and voltage drop. It does not rely on next-size-up overcurrent exceptions.

General-use ampacities are based on 2024 CEC Tables 2 and 4 for no more than three current-carrying conductors at 30°C before corrections. Ontario currently adopts the 2024 OESC, which combines the CEC with Ontario amendments. OESC information · CEC ampacity reference