Calculate AC motor power in watts, kW or hp from voltage, current and power factor for single- or three-phase motors, or solve for voltage, current or PF.

Uses RMS readings. This is electrical input power, not shaft output.

0.85 is a typical full-load value for induction motors; use the nameplate PF if you have it.

Optional settings

Related Calculators

AC Motor Power Formula

For single-phase supply, the AC motor power calculator uses the real electrical input power formula with RMS voltage and current (Three-phase multiplies it by √3):

P = V × I × PF

Rearranged formulas are used for the selected Solve for value:

V = P / (I × PF)
I = P / (V × PF)
PF = P / (V × I)
  • P = real power in watts (W)
  • V = voltage in volts (V)
  • I = current in amps (A)
  • PF = power factor, unitless

Choose the unknown under Solve for and enter the three known values. The calculator converts inputs to base units and reports the result with equivalent units. Use electrical input power, not rated shaft output.

  • Power calculation: uses voltage, current, and power factor to calculate watts, kilowatts, or horsepower.
  • Voltage calculation: uses power, current, and power factor to calculate the required voltage.
  • Current calculation: uses power, voltage, and power factor to calculate amperage.
  • Power factor calculation: uses power, voltage, and current to calculate the ratio of real power to apparent power.

Common AC Motor Unit Conversions

These are the unit conversions used when the calculator changes your entries into base electrical units.

Quantity Unit Equivalent
Power 1 kW 1000 W
Power 1 HP approximately 745.699872 W
Voltage 1 kV 1000 V
Current 1 mA 0.001 A
Current 1 kA 1000 A

Typical AC Motor Power Factor Values

Power factor depends on motor design, loading, and operating conditions. Use a measured value when you have one.

Motor condition Typical power factor range Meaning
Lightly loaded motor 0.30 to 0.60 Lower real power compared with apparent power
Moderately loaded motor 0.60 to 0.80 Common operating range for many motors
Near rated load 0.80 to 0.95 More efficient use of supplied current

AC Motor Power Examples

Example 1: Calculate power

You have a motor supplied with 230 V, drawing 8 A, with a power factor of 0.85.

P = V × I × PF
P = 230 × 8 × 0.85 = 1564 W

The motor power is 1564 W, or 1.564 kW.

Example 2: Calculate current

You have a motor drawing 2 kW of electrical input power on a 240 V supply with a power factor of 0.80.

First convert power to watts:

2 kW = 2000 W

Then calculate current:

I = P / (V × PF)
I = 2000 / (240 × 0.80) = 10.4167 A

The current is about 10.42 A.

FAQ

Does this calculator use single-phase or three-phase motor power?

Both. Choose Single-phase for P = V × I × PF, or Three-phase for a balanced motor with line voltage and line current, which uses P = √3 × V × I × PF.

What power factor should you enter for an AC motor?

Use the motor nameplate value or a measured value if available. If you do not have one, many loaded AC motors fall between about 0.80 and 0.95. A lightly loaded motor can have a much lower power factor, so an assumed value may only give an estimate.

Why is horsepower converted using approximately 745.7 watts?

The calculator uses the standard mechanical horsepower conversion of 1 HP = approximately 745.699872 W. This is a unit conversion only. Actual motor input power can be higher than shaft output power because motors are not 100% efficient.