Watts to kVA & VA Calculator
Convert real power in watts (W) to apparent power in kilovolt-amperes (kVA) and volt-amperes (VA) using power factor.
Convert Watts to kVA
Enter power in watts and power factor to find apparent power in kVA and VA.
How to Convert Watts to kVA
To convert watts to kVA, divide the real power in watts by the power factor, then divide by 1,000: kVA = W ÷ (PF × 1,000). Watts measure real (active) power, while kVA measures apparent power — the total power a transformer or UPS must deliver to the load.
Scenario: A 5,000 W server room with power factor 0.8
kVA = 5,000 ÷ 800
kVA = 6.25 kVA
You need at least a 6.25 kVA UPS or transformer.
Understanding kVA vs Watts vs VAR
In AC circuits, power has three components that form the Power Triangle:
| Power Type | Symbol | Unit | What It Measures |
|---|---|---|---|
| Real (Active) Power | P | Watts (W) | Useful work performed by the load |
| Apparent Power | S | VA or kVA | Total power the source must supply |
| Reactive Power | Q | VAR | Power stored/released by inductors and capacitors |
The relationship: S² = P² + Q² and PF = P ÷ S. Transformers and UPS systems are rated in kVA because they must handle the total current regardless of power factor.
Watts to kVA Conversion Table
Quick reference conversions at common power factors:
| Watts (W) | PF = 1.0 | PF = 0.9 | PF = 0.8 | PF = 0.7 |
|---|---|---|---|---|
| 1,000 W | 1.00 kVA | 1.11 kVA | 1.25 kVA | 1.43 kVA |
| 2,000 W | 2.00 kVA | 2.22 kVA | 2.50 kVA | 2.86 kVA |
| 5,000 W | 5.00 kVA | 5.56 kVA | 6.25 kVA | 7.14 kVA |
| 10,000 W | 10.00 kVA | 11.11 kVA | 12.50 kVA | 14.29 kVA |
| 20,000 W | 20.00 kVA | 22.22 kVA | 25.00 kVA | 28.57 kVA |
| 50,000 W | 50.00 kVA | 55.56 kVA | 62.50 kVA | 71.43 kVA |
Frequently Asked Questions About Watts to kVA Conversion
What is the difference between watts and kVA?
Watts measure real (active) power — the actual work performed by a device. kVA measures apparent power — the total power a source must provide, including reactive power from inductors and capacitors. In purely resistive loads (PF = 1.0), watts equals kVA. In inductive loads like motors (PF < 1.0), kVA is always greater than watts.
How do I convert kVA to watts?
To convert kVA to watts: Watts = kVA × PF × 1,000. For example, a 10 kVA generator at PF 0.8 delivers 10 × 0.8 × 1,000 = 8,000 W of real power. The remaining apparent power (2 kVA) is reactive and does not perform useful work.
Why are transformers rated in kVA instead of watts?
Transformers are rated in kVA because their losses depend on current (I²R copper losses) and voltage (core iron losses), not on the load power factor. A 10 kVA transformer supplies the same current whether the load has PF 1.0 or PF 0.5. The transformer does not know or control the load's power factor, so its capacity is expressed in apparent power (kVA).
What power factor should I use for a UPS?
Modern UPS systems typically have output power factor of 0.9 or 1.0. A 10 kVA UPS with PF 0.9 delivers 9,000 W. Older UPS models may have PF 0.6–0.8. Always check the UPS datasheet for the rated output power factor to determine available watts.
Is 1 kVA equal to 1000 watts?
1 kVA equals 1,000 watts only when power factor is 1.0 (purely resistive load). In most real-world AC circuits with motors, fluorescent lights, or switched-mode power supplies, PF < 1.0, so 1 kVA provides less than 1,000 watts of usable power. At PF 0.8, 1 kVA = 800 W.
How do I size a generator using watts and kVA?
To size a generator: first calculate total watts needed, then divide by power factor to get required kVA. If total load is 8,000 W with PF 0.8: kVA = 8,000 ÷ 0.8 ÷ 1,000 = 10 kVA. Add 20–25% safety margin: choose a 12–13 kVA generator to handle startup surges.