Generators, transformers and UPS units are rated in kVA because their heating depends on current, not on the load’s power factor. The kW they can deliver depends on the PF of what you connect.
How to use the kVA Calculator
- Phase
- Voltage
- Current
- Power factor
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the phase, enter the voltage and current, and optionally the power factor.
Inputs explained
| Field | What to enter |
|---|---|
| Phase | Choose one: Single-phase, Three-phase |
| Voltage | Units: V, kV, mV |
| Current | Units: A, mA, µA, kA |
| Power factor | A number |
Example values
How the main result changes when Voltage changes and everything else stays at the example values above:
| Voltage (V) | Apparent power (kVA) |
|---|---|
| 200 | 10 |
| 300 | 15 |
| 400 | 20 |
| 500 | 25 |
| 600 | 30 |
| 800 | 40 |
Formula
1-phase: S = V·I/1000 · 3-phase: S = √3·V_LL·I/1000, P = S·PF
Worked example
Inputs — Phase: Single-phase; Voltage: 400 V; Current: 50 A; Power factor: 0.8.
Results — Apparent power = 20 kVA; Real power = 16 kW.
Key terms
- kVA
- Kilovolt-ampere, a unit of apparent power.
Frequently asked questions
What is the difference between kVA and kW?
kVA is apparent power; kW is real power (kVA × PF).
Why are transformers rated in kVA?
Their losses depend on current regardless of power factor.
What PF do generators assume?
Usually 0.8.
How many amps is a 100 kVA three-phase at 400 V?
About 144 A.