Calculate AC motor power, voltage, current, or power factor from any 3 inputs, with unit conversions for watts, kW, HP, volts, kV, amps, mA, and kA.
Customize This Calculator
Build your own version. Describe what you want changed, added, or compared.
Related Calculators
- Active Power Calculator
- Over Load Current Calculator
- Power Supply Efficiency Calculator
- Annual Energy Production Calculator
- All Physics Calculators
AC Motor Power Formula
The AC motor power calculator uses the real power formula for an AC circuit with power factor:
Rearranged formulas are used when you leave a different field blank:
- P = real power in watts (W)
- V = voltage in volts (V)
- I = current in amps (A)
- PF = power factor, unitless
Enter any three values and leave the fourth blank. The calculator converts the selected units to base units, applies the matching formula, then converts the result back to the unit you selected.
- 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 | 746 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.
The motor power is 1564 W, or 1.564 kW.
Example 2: Calculate current
You have a 2 kW motor on a 240 V supply with a power factor of 0.80.
First convert power to watts:
Then calculate current:
The current is about 10.42 A.
FAQ
Does this calculator use single-phase or three-phase motor power?
This calculator uses the formula P = V × I × PF. That matches single-phase real power, or a simplified equivalent calculation when voltage and current are already expressed in compatible total values. For a standard balanced three-phase motor using line voltage and line current, the usual formula includes an additional factor of √3.
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 746 watts?
The calculator uses the standard mechanical horsepower conversion of 1 HP = 746 W. This is a unit conversion only. Actual motor input power can be higher than shaft output power because motors are not 100% efficient.