Electrical · Updated 3 October 2026
kW, kVA and amps: choosing the right calculation
Understand active power, apparent power, power factor and line current before converting a motor or equipment rating.
Read the unit before choosing a calculator
A kW rating describes active power. A kVA rating describes apparent power. Amps describe current. These quantities are related, but a power rating alone does not tell you the current: the supply voltage and phase arrangement also matter.
Use the kVA calculator for an apparent-power rating. Use the kW calculator for electrical active input power and enter the load power factor. Do not put a kVA value in the kW field.
How power factor changes the conversion
For AC power, kW = kVA × power factor. Single-phase current is kW × 1000 ÷ (voltage × power factor). Balanced three-phase line current is kW × 1000 ÷ (√3 × line-to-line voltage × power factor).
Enter power factor as a decimal greater than zero and no higher than one. A percentage must be divided by 100 before entry. Use voltage measured or specified for the same operating condition as the power rating.
Motor shaft power needs another step
A motor nameplate can state mechanical output power. Electrical input power is output power divided by efficiency expressed as a decimal. Convert horsepower to kW first if needed, then distinguish shaft output from electrical input before calculating current.
Checks before using the result
- Confirm that three-phase voltage is line-to-line, not line-to-neutral.
- Record the equipment rating, voltage, power factor and source of each value together.
- Compare the result with the equipment documentation or a suitable measurement.
- Use a separate design process for cables, protection and starting conditions. A load-current result does not specify a breaker size.