CEC Part I · Rule 8-104 (Continuous Loads)

Breaker Size Calculator

Watts or amps in — minimum standard breaker size out, with the 125% continuous-load rule built in.

1. Load Details

Enter Watts

Enter Amps

Load (W)

Load (A)

Circuit Voltage

Continuous load (runs 3+ hours at a stretch — EV chargers, space heaters, etc.)

2. Minimum Breaker

Standard load

CALCULATED CURRENT

— A

MINIMUM STANDARD BREAKER

— A

Note: Enter a load to see the minimum breaker size.

This tells you the minimum breaker, not the wire. Check the required conductor size for this breaker with our Wire Size Calculator before pulling cable.

Why continuous loads get sized at 125%

A "continuous load" runs at or near full draw for 3 hours or more — EV chargers, space heaters, and some shop equipment are common examples.
The CEC requires continuous loads to be sized at 125% of their rated current for both the breaker and the conductor, to prevent nuisance tripping and long-term heat buildup.
Standard intermittent loads (most lighting and receptacle circuits) don't need this margin.

From load to breaker

Standard breaker sizes & max continuous load (80% rule)

CEC 14-010 standard sizes — a breaker may carry only 80% of its rating continuously (3+ hours).

Breaker	Max continuous	Typical use
15 A	12 A	Lighting, bedroom receptacles
20 A	16 A	Kitchen counters, bathroom receptacles
30 A	24 A	Dryer, baseboard heaters, water heater
40 A	32 A	Range, larger AC units
50 A	40 A	Range, hot tub (with GFCI), EV charger
60 A	48 A	Subpanel feeder, large EV charger
100 A	80 A	Main service (small home), garage feeder

The calculator applies the 125% continuous-load rule and rounds up to the next standard size automatically.

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