VA to Watts Calculator
Convert volt-amperes to real power in watts or kilowatts.
How do you convert VA to watts?
Multiply VA by the power factor: watts = VA × PF. A 500 VA power supply at a 0.9 power factor delivers 500 × 0.9 = 450 W of real power. For purely resistive loads the power factor is 1, so volt-amperes and watts are equal.
VA to Watts Formula
Example: 2,000 VA × 0.85 PF = 1,700 W
Example: 2,000 VA × 0.85 PF = 1.7 kW
The power triangle shows three related quantities: apparent power (VA), real power (W), and reactive power (VAR). The power factor is the cosine of the angle between apparent and real power: PF = W ÷ VA. A PF of 1.0 means all apparent power is doing useful work; a lower PF means some power is being stored and returned by reactive components (inductors, capacitors) rather than consumed.
Working with kilovolt-amperes instead? See our kVA to kW Calculator to
VA to Watts — UPS Reference Table
| VA Rating | PF 0.6 | PF 0.7 | PF 0.8 | PF 0.9 | PF 1.0 |
|---|---|---|---|---|---|
| 500 VA | 300 W | 350 W | 400 W | 450 W | 500 W |
| 650 VA | 390 W | 455 W | 520 W | 585 W | 650 W |
| 1,000 VA | 600 W | 700 W | 800 W | 900 W | 1,000 W |
| 1,500 VA | 900 W | 1,050 W | 1,200 W | 1,350 W | 1,500 W |
| 2,000 VA | 1,200 W | 1,400 W | 1,600 W | 1,800 W | 2,000 W |
| 3,000 VA | 1,800 W | 2,100 W | 2,400 W | 2,700 W | 3,000 W |
| 5,000 VA | 3,000 W | 3,500 W | 4,000 W | 4,500 W | 5,000 W |
| 10,000 VA | 6,000 W | 7,000 W | 8,000 W | 9,000 W | 10,000 W |
PF 0.8 column highlighted — the most common default for general estimation.
VA vs Watts: What's the Difference?
VA is the total power drawn from the supply, combining both real power (doing useful work) and reactive power (stored and returned by inductors and capacitors). Cables, fuses, circuit breakers, UPS units, and transformers must all be sized to handle the full VA load — not just the watts.
VA = W ÷ PFWatts measure the actual work performed: generating heat, light, or mechanical motion. This is what your electricity meter measures and what you are billed for. For resistive loads like heaters and incandescent bulbs, VA and watts are identical. For inductive loads (motors, transformers, UPS), watts are always less than VA.
W = VA × PFWhy VA Doesn't Equal Watts in Real Life
Volt-Amps (VA) is the "apparent power" your wiring must carry, while Watts is the "real power" your device actually uses to do work. The difference between them is the power factor. Here are common electronics and how their VA rating translates to actual Watts:
| Device Type | Power Factor (PF) | 1000 VA Input Translates To... |
|---|---|---|
| Incandescent Bulb / Resistive Heater | 1.0 | 1,000 Watts (Perfect efficiency) |
| Modern PC Power Supply (Active PFC) | 0.95 - 0.99 | 950 - 990 Watts |
| Cheap AC/DC Wall Adapter (No PFC) | 0.50 - 0.60 | 500 - 600 Watts |
| Unloaded AC Motor / Fan | 0.40 - 0.70 | 400 - 700 Watts |
This matters most for Uninterruptible Power Supplies (UPS). If you buy a 1000 VA UPS to power a cheap power supply (PF 0.6), the UPS might max out its hardware limits providing 1000 VA, even though your PC is only doing 600 Watts of work.
Frequently Asked Questions
W = VA × PF, where PF is the power factor (a number between 0 and 1). For a 1,500 VA UPS with a power factor of 0.6: W = 1,500 × 0.6 = 900 W. For resistive loads (PF = 1), VA equals watts exactly.
No. VA (volt-amperes) is apparent power — the total power drawn from the supply, including reactive power from inductive or capacitive loads. Watts is real power — the portion that does actual work. They are equal only when the power factor is 1.0 (purely resistive loads like incandescent bulbs and simple heaters). For motors, UPS systems, and most electronics, PF < 1, so VA > watts.
It depends on the UPS power factor. Older UPS units: PF ≈ 0.6 to 1,500 × 0.6 = 900 W. Modern online double-conversion UPS units: PF ≈ 0.9 to 1,500 × 0.9 = 1,350 W. Check the UPS datasheet for the rated power factor.
Common values: 0.6 for older UPS units (offline/line-interactive type), 0.7–0.8 for industrial motors, 0.8–0.9 for modern UPS (double-conversion), 0.9–0.95 for large commercial HVAC, 1.0 for resistive loads (heaters, incandescent lights). When in doubt, use 0.8 as a conservative estimate.
Check the device datasheet or the label on the back panel — it is often listed as "PF" or "cos φ". If not listed, use a power meter (such as a Kill-A-Watt device) to measure VA and watts simultaneously; PF = W ÷ VA. For UPS systems, the power factor is always specified in the product specifications.
If my device uses 500 Watts, is a 500 VA UPS big enough?
Usually not. If your device has a power factor of 0.8, it requires 625 VA of apparent power to deliver those 500 Watts (500 ÷ 0.8). A 500 VA UPS would be overloaded. Always buy a UPS with a VA rating 20-30% higher than your actual Wattage requirement.