About the Watts to kVA Calculator
This calculator converts W to kVA. W is one joule of energy per second, the basic unit of power printed on bulbs, chargers and appliances, and kVA is a thousand volt-amperes, the apparent power rating of transformers, generators and UPS units. It divides the watts by the power factor and by 1,000. Enter your figures and the answer appears at once, together with a few related values, and you can copy the result with one tap. The sums are done in your browser and nothing is sent anywhere.
Updated October 2026
How to use the Watts to kVA Calculator
- 1Enter the value in W.
- 2Fill in the other boxes that the W to kVA calculation needs, such as time, voltage or power factor.
- 3Read the answer in the large result box.
- 4Check the extra rows for related values.
- 5Press Copy result to keep it.
When you need W to kVA
Transformers and generators are sold by kVA, but when you list the loads they will carry, the numbers are in watts. Divide the total watts by the power factor, then by a thousand, to find the kVA rating you need. This tool does it in one go.
Contractors use it to size a temporary supply on a building site, electricians to check the capacity of a distribution board, and students to practise power calculations in AC circuits.
How the W to kVA sum works
kVA = watts ÷ power factor ÷ 1,000. A 4,000 W load at a power factor of 0.8 needs 4,000 ÷ 0.8 ÷ 1,000 = 5 kVA.
The displayed answer is rounded to six significant figures, but the sum itself is not rounded, so converting W to kVA and back again gives you the number you started with.
- Add up simultaneous loads
- Include a margin
- Use the actual power factor
Mistakes to avoid when converting W to kVA
Remember to add all loads that can run at the same time, and then a margin for growth and starting surges. Using only the typical load can lead to a unit that trips under peak demand.
On phone and computer
On a phone, type in the boxes one after another and read the kVA result underneath; the Copy button puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the kVA value move. The W to kVA page works the same on both. The answer changes with the power factor, so reverse it with kVA to kW Calculator. kW to kVA Calculator takes kilowatts directly, Watts to VA Calculator uses small units, and Amps to kVA Calculator starts from a current reading.
Features
- W to kVA in one step
- Related values shown with the answer
- Clear messages for impossible inputs
- Copy the result with one tap
- Private: nothing is uploaded
- Works on phone and computer
Frequently asked questions
How do I convert W to kVA?
kVA = watts ÷ power factor ÷ 1,000. A 4,000 W load at a power factor of 0.8 needs 4,000 ÷ 0.8 ÷ 1,000 = 5 kVA.
What is the formula for W to kVA?
kVA = watts ÷ power factor ÷ 1,000. The calculator applies it exactly and rounds only the displayed answer.
What is the difference between W and kVA?
W is one joule of energy per second, the basic unit of power printed on bulbs, chargers and appliances. kVA is a thousand volt-amperes, the apparent power rating of transformers, generators and UPS units. They measure different things, which is why converting from W to kVA needs more than a simple multiplication in some cases.
How many kVA is 4,000 watts?
At a power factor of 0.8 it is 5 kVA. At a power factor of 1 it is 4 kVA.
Is kVA always bigger than kW?
Yes, or equal. kVA equals kW only when the power factor is 1.
Is this W to kVA calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so the figures you type are not uploaded or stored. It is meant for planning and learning; for wiring or safety work, check the result against your equipment's rating plate and local rules.