ProjectFigure Exact material estimates for every home & DIY project.

kVA Calculator

A kVA calculator converts apparent power (kVA) into full-load current (amps) and real power (kW), for single- or three-phase systems. It's the tool for sizing a transformer, generator or service from a load — or for reading the amps a rated unit can deliver.

Your measurements

Result

Generators and transformers are rated in kVA, but breakers and wire are sized in amps, so you constantly need to convert between them. This does it with the right √3 factor for three-phase and the power factor for kW.

How it is calculated

Single-phase: amps = kVA × 1000 ÷ V. Three-phase: amps = kVA × 1000 ÷ (√3 × V), using line-to-line voltage. Real power kW = kVA × power factor. kVA (apparent) is what generators and transformers are rated in; kW is the usable real power.

Steps

Enter the apparent power in kVA.
Enter the line-to-line voltage.
Choose single- or three-phase.
Set the power factor (≈0.8 typical, 1.0 resistive).
Read the full-load amps and the real power in kW.

Worked example

A 10 kVA single-phase unit at 240 V delivers about 42 A; at PF 0.8 that's 8 kW of real power.

Common questions

How do I convert kVA to amps?

Single-phase: kVA × 1000 ÷ volts. Three-phase: kVA × 1000 ÷ (1.732 × volts). The calculator handles both.

What's the difference between kVA and kW?

kVA is apparent power (volts × amps); kW is real power that does work. kW = kVA × power factor.

How do I size a generator?

Add up the running kVA (or watts) of your loads, allow for motor start-up surge, and pick a generator rated above that. Convert to amps to check the breaker.

Why the √3 in three-phase?

Three-phase power combines three windings; the line current relates to power through the √3 (1.732) factor at the line-to-line voltage.