About the Amps to kVA Calculator
Transformers, generators and UPS units are rated in kilovolt-amperes because the supply has to carry the full current whatever the power factor of the load. This calculator converts a current in amps to kVA for single-phase and three-phase supplies by multiplying by the voltage, and by the square root of three for three-phase, and dividing by 1,000. If you add the power factor, it also shows the real power in kilowatts, so you can compare a load with a generator's rating in both kVA and kW.
Updated October 2026
How to use the Amps to kVA Calculator
- 1Choose single-phase or three-phase.
- 2Enter the current in amps.
- 3Enter the voltage. For three-phase use the line-to-line voltage.
- 4Optional: enter the power factor to see the real power in kW.
- 5Read the apparent power in kVA and VA.
Worked examples
A single-phase supply of 63 amps at 230 volts is 14.5 kVA. A three-phase supply of 100 amps at 400 volts is 69.3 kVA. If the load has a power factor of 0.85, the real power is about 58.9 kW. Compare that with the nameplate of the generator to see whether it has enough capacity in both kVA and kW.
Remember that kVA ratings are quoted at a stated voltage and often at a stated temperature and altitude. A generator that is rated 20 kVA at sea level may deliver less in hot weather or high up a mountain, and a transformer loses capacity if the ambient temperature is very high. Use the calculator for the electrical sum, then check the manufacturer's derating tables if your site conditions are unusual or if the load will run for long periods near the limit.
Standard ratings
- Small portable generators: 2 to 10 kVA.
- Standby generators for homes: 10 to 30 kVA.
- Distribution transformers: 25 to 2,500 kVA.
- Typical UPS units: 1 to 20 kVA.
- Large industrial generators: 500 kVA and above.
Next steps
Use the kVA to kW Calculator and the Power Factor Calculator to move between apparent and real power, the VA to Watts Calculator for smaller loads and the Amps to Watts Calculator for DC. The Voltage Drop Calculator checks that cables are not too long for your current.
Features
- kVA and VA from amps
- Single-phase and three-phase
- Optional real power in kW
- Matches generator and transformer ratings
- Handles any voltage
- Free, private, instant
Frequently asked questions
What is the formula for converting amps to kVA?
For single-phase, kVA equals amps times volts divided by 1,000. For three-phase, kVA equals amps times line voltage times 1.732 divided by 1,000. A 50 amp three-phase load at 415 volts is about 35.9 kVA.
What is the difference between kVA and kW?
kVA is the apparent power, which determines the current and the size of cables and equipment. kW is the real power that does useful work. kW equals kVA times the power factor, so a 100 kVA load at 0.8 is 80 kW.
How do I choose a generator size from amps?
Convert the maximum running current to kVA, add a margin for starting currents, often 25 percent or more for motors, and choose the next standard generator size. Check whether the generator's kW rating also covers the real power.
Why do transformers use kVA?
A transformer's heating depends on the current it carries, not on the power factor. The same transformer can feed any load up to its kVA rating, but it supplies fewer kilowatts to a poorly corrected load.
Can I convert DC amps to kVA?
Not in the usual sense. Volt-amperes and the power factor belong to AC. For DC, watts are simply amps times volts, so use the Amps to Watts Calculator.
Does the calculator account for cable losses?
No. It uses the voltage you enter at the load. If cables are long, the voltage at the equipment may be lower than at the source, which the Voltage Drop Calculator can estimate.