Energy

Transformer Load Calculator

Calculate transformer loading, actual kVA demand, remaining capacity and full-load current.

Electrical System

Transformer Rating

Voltage

Enter line-to-line voltage for a three-phase transformer.

Load Current

Power Factor

Optional. Used only to estimate real power in kW.

Transformer Loading

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Apparent load relative to the transformer nameplate kVA rating.

Actual apparent load —

Transformer loading —

Remaining capacity —

Full-load current —

Estimated real power —

Transformer rating —

System —

Method: For a balanced three-phase system: S = √3 × V × I For single-phase: S = V × I Transformer loading is: Loading (%) = actual apparent power ÷ transformer rated apparent power × 100 Full-load current for a three-phase transformer is: I = rated VA ÷ (√3 × V) For single-phase: I = rated VA ÷ V If power factor is entered: P = S × PF where P is real power in kW. Transformer loading is fundamentally based on apparent power in kVA, not only real power in kW. Nameplate rating alone does not determine whether continuous operation at a particular load is acceptable. Ambient temperature, cooling class, harmonics, load profile, altitude, transformer temperature rise and manufacturer limits can affect permissible loading.