Electrical & Lighting · Conversion · Free

Watts to VA Calculator

Convert real power in watts (W) to apparent power in volt-amps (VA). Enter the power in watts and the power factor, and press Calculate to get volt-amps using S(VA) = P(W) / PF. Everything runs locally in your browser.

STEP 1

Enter the watts

Type the real power P in watts (W) — the power actually consumed by the load, as printed on the device nameplate or measured by a wattmeter.

STEP 2

Enter the power factor

Type the power factor PF, a number greater than zero — typically between 0 and 1 (a resistive heater is 1, an induction motor is often around 0.8). PF = 0 is rejected because division by zero has no result.

STEP 3

Press Calculate, read volt-amps

The result appears in volt-amps (VA), rounded to at most three decimals. Press Reset at any time to clear the fields and start over.

Watts to VA calculation

How do you convert watts to VA?: The apparent power S in volt-amps (VA) is equal to the real power P in watts (W), divided by the power factor PF: S(VA) = P(W) / PF. For example, a 1200 W load at a power factor of 0.8 draws S = 1200 / 0.8 = 1500 VA.
What is the power factor?: The power factor is the ratio of real power (W) to apparent power (VA) — how much of the drawn current actually does useful work. It is typically between 0 and 1: resistive loads like heaters and incandescent lamps have PF ≈ 1, while motors, transformers, and many electronics sit lower, often around 0.6 to 0.9.
When are watts and VA equal?: At a power factor of 1 the two are identical: S = P / 1 = P. A 100 W resistive load at PF = 1 is exactly 100 VA. The lower the power factor, the larger the apparent power for the same real power.
Why size equipment in VA instead of watts?: UPS units, transformers, and generators must carry the full apparent current, not just the useful part. A 1200 W server at PF 0.6 needs 1200 / 0.6 = 2000 VA of capacity, which is why VA ratings are always at least as high as the wattage.
Worked example: A 1000 W motor at a power factor of 0.7 draws S = 1000 / 0.7 ≈ 1428.571 VA. If the same motor runs at PF 1, it would draw just 1000 VA — the gap is the reactive power circulating without doing work.

Privacy: every calculation runs in your browser tab — no value you type is sent anywhere, and this tool does not use the clipboard, storage, or the network. Results assume a constant power factor; verify real installations with a power analyzer.