Calculator InputLive calculation
kW to Amps Motor Calculator
Pre-configured for three-phase AC circuits. Adjust values below.
Conversion Result
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Enter values to calculate
Formula Used
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Watts
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Milliamps
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Horsepower
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BTU/hr
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How kW to Amps Motor Works
1
Enter the motor power in kW
Use the nameplate kW rating. If the motor is rated in HP, convert: 1 HP = 0.746 kW.
2
Enter the supply voltage
Check the motor nameplate for voltage rating. Common values: 220V, 380V, 400V, 415V, 440V, 480V.
3
Enter the power factor
Motor PF is shown on the nameplate. Typical values: 0.80 at full load for small motors, 0.85–0.90 for large motors.
4
Read the full-load amps (FLA)
This is the current the motor draws at full mechanical load. Use this for cable sizing, starter selection, and overload relay settings.
kW to Amps Motor Formula
3-Phase MotorI = (kW × 1000) ÷ (√3 × V × PF)
Standard formula for three-phase induction motors.
From HPI = (HP × 746) ÷ (√3 × V × PF × η)
Includes motor efficiency (η). Typical η: 0.85–0.95.
Starting CurrentI_start ≈ FLA × 6 to 8
Induction motors draw 6–8× full-load amps during starting (DOL start).
The motor kW to amps formula is I = (kW × 1000) ÷ (√3 × V × PF) for three-phase motors.
For example, a 7.5 kW motor at 415V with PF 0.85 draws: I = (7.5 × 1000) ÷ (1.732 × 415 × 0.85) = 12.28 amps at full load.
Motor current calculations are essential for selecting the correct overload relay, contactor, cable size, and circuit breaker. The NEC requires that motor branch-circuit conductors be sized at 125% of the motor full-load current (NEC 430.22).
Frequently Asked Questions
A 5.5 kW three-phase motor at 415V with PF 0.85 draws 9.00 amps at full load.
FLA is the current a motor draws when delivering its rated mechanical output at rated voltage. It is listed on the motor nameplate.
Multiply HP by 0.746. Example: 10 HP = 7.46 kW. Then use the kW to amps formula.
At startup, the rotor is stationary and presents very low impedance, causing high inrush current (6–8× FLA). As the motor accelerates, current drops to the FLA value.
Motor PF drops at partial load. At 50% load, PF may be 0.65–0.75. At 25% load, PF may drop to 0.50–0.60. VFDs can improve partial-load efficiency.