Convert Volt-Ampere to Watt (VA → W)

Converting volt-amperes to watts is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in volt-amperes

   Start with the number of volt-amperes (VA) you want to convert.
2. 2
   Multiply by 1

   The conversion factor from VA to W is 1. Multiply your value by this number.
3. 3
   Read the result in watts

   The result is your value in watts (W).

Multiply the value in volt-amperes by 1. For the reverse direction, multiply by 1.

• ✓VA = V × A (RMS).
• ✓For purely resistive loads, VA = W.
• ✓For motors, computers: VA > W (power factor < 1).

• ✗Treating VA and W as identical — only true for resistive loads.
• ✗Buying UPS by W when VA rating is required.
• ✗Ignoring power factor in transformer sizing.

What is the Volt-Ampere?

The volt-ampere (VA) is the SI unit of apparent power in alternating-current (AC) electrical systems. Equal to volts times amperes, the VA represents the magnitude of power flowing in an AC circuit before accounting for the phase relationship between voltage and current. For purely resistive loads (incandescent bulbs, heaters), 1 VA = 1 W. For reactive loads (motors, transformers, fluorescent lights), the apparent power (VA) is larger than the real power (W) because of the phase shift — the ratio is the 'power factor.' Transformers, UPS units, and generators are rated in VA or kVA (kilo-VA) because they must handle the apparent power, not just the real power. A typical home UPS for a desktop computer is 600–1,500 VA. The VA relates to the watt (1 VA = 1 W only at unity power factor), the kilovolt-ampere (1 kVA = 1,000 VA), and the megavolt-ampere (1 MVA = 10⁶ VA — used in utility-scale transformers).

• Transformer sizing
• Uninterruptible power supply (UPS) ratings
• Generator capacity

What is the Watt?

The watt is the SI unit of power, equal to one joule per second (1 W = 1 J/s). Named after Scottish engineer James Watt (1736–1819), whose improvements to the steam engine sparked the Industrial Revolution, the watt unifies mechanical, electrical, and thermal power. A typical LED bulb consumes 8–12 W to produce as much light as a 60-W incandescent bulb. Human resting metabolism is about 80–100 W of heat output, while peak athletic performance reaches 400–1,500 W (briefly). The watt is fundamental in electrical engineering: P = V × I (power = voltage × current). It relates to the kilowatt (1 kW = 1,000 W), the megawatt (1 MW = 10⁶ W), horsepower (1 hp ≈ 745.7 W), and the BTU per hour (1 W ≈ 3.412 BTU/h). Light bulb and appliance ratings, electric motor outputs, and audio amplifier specifications all use the watt as the base unit.

• Light-bulb and appliance ratings
• Scientific and engineering power specs
• Radio and electronics power