By Sarah Arianrhod • Updated March 24, 2022

Calculating kilovolt‑amps (kVA) from three‑phase kilowatts (kW) is essential for sizing motors, generators, and protection devices. The calculation hinges on the power factor (PF), a dimensionless ratio that reflects how efficiently a circuit converts electrical power into useful work.

Use the formula below to determine the apparent power a three‑phase device requires:

kVA = kW ÷ PF

Step 1 – Identify the kW Input

Obtain the rated power of the motor or appliance from its nameplate or the manufacturer’s data sheet. This value represents the real power the device consumes.

Step 2 – Determine the Power Factor

Most nameplates list the PF directly. If it’s not displayed, consult the equipment specifications or measure it with a calibrated ammeter and voltmeter: PF = real power ÷ apparent power.

Step 3 – Compute the kVA

Divide the kW value by the PF. For example, a motor rated at 720 kW with a PF of 0.60 yields:

kVA = 720 kW ÷ 0.60 = 1,200 kVA

Because kVA always exceeds kW, this result reflects the unavoidable losses in the system.

What You’ll Need

• Calculator (for quick mental math)
• Hand‑held digital multimeter or clamp ammeter (optional but improves accuracy)

Important Notice

Manufacturer’s ratings can differ from real‑world consumption. For critical applications, take in‑service measurements with a calibrated ammeter to ensure precise kVA sizing and to protect equipment from over‑ or under‑loading.