Your result will appear here.
Estimate main breaker size from connected load, demand load, voltage, phase type, continuous load factor, and planning target. This calculator helps compare demand amps to common main breaker and service sizes.
Demand amps:
The calculator either uses manual demand amps or estimates demand amps from detailed load inputs.
Planning target:
The demand amps are divided by the selected planning target, such as 80%, 90%, or 100%.
Breaker selection:
The result is rounded up to a common main breaker or service size.
A main breaker size calculator helps estimate the service-size range needed for a home, shop, garage, outbuilding, or small building.
It can help with service upgrade planning, panel replacement planning, EV charger planning, HVAC upgrades, subpanel planning, appliance additions, and general electrical capacity estimates.
Your result shows recommended main breaker size, main breaker size at your planning target, demand amps, connected load, demand load, existing breaker load percentage, remaining capacity, and comparison scenarios.
Estimate the calculated demand load, convert it to amps, then select a main breaker and service equipment size that can safely handle the demand load with the required margin.
Not unless the panel, meter base, service conductors, grounding, utility service, and code requirements all support the larger size. Upsizing a main breaker without verification can be dangerous.
They are closely related. The main breaker often reflects the service rating, but the full service rating also depends on service conductors, meter equipment, panel rating, and utility requirements.
No. This is a simplified planning tool. Official main breaker and service sizing depends on electrical code, utility requirements, equipment nameplates, demand factors, service conductors, permits, and inspection rules.