About the Electrical Sizing Calculators
Electrical sizing calculators help HVAC engineers and electricians determine the correct wire gauge, circuit breaker size, and electrical service requirements for mechanical equipment. This collection covers minimum circuit ampacity (MCA), maximum overcurrent protection (MOCP), wire sizing based on amperage and distance, and single- and three-phase power calculations per the National Electrical Code. Use these tools when preparing electrical submittals, coordinating with electricians on panel schedules, or verifying that existing circuits can support new or replacement equipment. Each calculator follows NEC guidelines and standard voltage-drop formulas so results are consistent with what inspectors and plan reviewers expect. They eliminate the need for manual table lookups and reduce the risk of undersized conductors or improperly rated breakers.