Motor FLA & Starter Calculator

Calculate motor full-load current, starting current for different methods, and get contactor + overload relay sizing recommendations.

Enter values and calculate

Starting Method Comparison

Method Starting Current (A) Reduction Status

Formulas Used

Full-Load Current (Three Phase)

FLA = (kW × 1000) / (√3 × V × η × PF)

Full-Load Current (Single Phase)

FLA = (kW × 1000) / (V × η × PF)

Contactor Sizing

Contactor ≥ 1.25 × FLA

Overload Relay Setting

OLR range must contain 1.05 × FLA

Learn More:

Star-Delta Starter — Working Principle & Connection Diagram
Starting Methods of Induction Motor — DOL, Star-Delta, VFD
Function of Starter in DC Motor
What is VFD? — Working Principle & Applications

Starting Current Assumptions

• DOL: 6× FLA (locked rotor current)
• Star-Delta: 2× FLA (⅓ of DOL due to √3 voltage reduction)
• Soft Starter: 3× FLA (adjustable 1.5–4×, typical setting)
• VFD: 1.2× FLA (current-limited ramp)

• Contactor sized at ≥ 1.25 × FLA (AC3 duty)
• Overload relay: nearest standard range containing 1.05 × FLA
• Standard induction motor assumed
• Balanced three-phase supply
• Motor at rated nameplate conditions