How do I calculate motor full-load current from nameplate?

For 3-phase: I = P / (√3 × V × cos φ × η). For 1-phase: I = P / (V × cos φ × η). Where P is rated power in watts, V is voltage, cos φ is power factor, and η is efficiency.

What is the difference between nameplate kW and electrical input kW?

Nameplate kW is the mechanical output power at the shaft. Electrical input = nameplate kW / η. The current drawn from the supply is based on the electrical input power, not the shaft output.

What are typical motor efficiency values?

IE1: 82-90%, IE2: 85-92%, IE3: 87-95%, IE4: 90-96%. Efficiency depends on motor size — larger motors are more efficient. Always use the nameplate value if available.

Why does my measured current differ from calculated?

Common reasons: motor not at full load (current is proportional to load), supply voltage differs from nameplate, ambient temperature affects winding resistance, harmonics from VFD supply.

Can I use this for DC motors?

For DC motors: I = P / (V × η). No power factor term since DC has no reactive component. This calculator supports DC mode selection.

Free Engineering Tool

Motor Nameplate Current Calculator

Calculate full-load amps (FLA) from motor nameplate data. Supports 3-phase and 1-phase motors.

3-Phase1-PhaseIEC 60034

Results

Full-Load Current (FLA)

—

Electrical Input Power

—

Apparent Power S

—

Phase Configuration

—

Motor Nameplate Current Calculator

Results

3-Phase Motor Current

1-Phase Motor Current

Motor Nameplate Current Calculator | FLA from Power | Free Online Tool

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Results

3-Phase Motor Current

1-Phase Motor Current