kVA to Amps Calculator: Single and Three-Phase
Convert kVA to amps for single-phase and three-phase supplies from the line-to-line voltage. Shows I = 1000 × kVA ÷ (√3 × V) with transformer and generator examples.
Fill in every field to see the result.
Results are ideal-circuit estimates: they ignore wire resistance, reactance and losses. In three-phase circuits the voltage is the line-to-line voltage.
About the kVA to Amps Calculator
The kVA to Amps Calculator turns the apparent power rating of a transformer, generator or UPS into the current it can supply. Type the rating in kVA, choose single-phase AC or three-phase AC, and type the voltage. The page opens on the power converter with kVA to amps already selected. You can also convert amps back to kVA, or kVA to kW with a power factor.
Transformers and generators are rated in kVA rather than kW because their limit is the current their windings can carry, whatever the power factor of the load. The kVA figure therefore converts straight into a current without a power factor. To know how much real power, in kW, the machine can deliver, multiply the kVA by the power factor of the load.
The result is an ideal estimate of the full-load current. It does not include derating for heat, altitude or harmonics, which a manufacturer's datasheet gives.
The formulas
With S the apparent power in kVA and V the voltage:
In three-phase systems, V is the line-to-line voltage, measured between two phases. Using the line-to-neutral voltage (230 V instead of 400 V) by mistake gives a current that is √3 times too high.
Real power is kW = kVA × PF.
Worked examples
Single-phase generator
A 10 kVA generator on 240 V supplies up to 10,000 ÷ 240 = 41.6667 A.
Three-phase transformer
A 50 kVA transformer at 400 V supplies 50,000 ÷ (√3 × 400) = 72.1688 A per line. At 480 V the same rating gives 60.1407 A.
kVA to kW
A 50 kVA generator feeding loads with a power factor of 0.8 delivers 50 × 0.8 = 40 kW of real power. That 0.8 figure is the usual assumption on generator rating plates.
Common three-phase values at 400 V
15 kVA is 21.65 A, 25 kVA is 36.08 A, 75 kVA is 108.25 A, 100 kVA is 144.34 A, 500 kVA is 721.69 A and 1,000 kVA is 1,443.38 A per line.
Choosing a size
Add up the running current of every load, allow for motor starting surges, and leave headroom of around 20 to 25 percent. A local electrician or the supplier's sizing guide decides the final rating.
Privacy
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Related tools
Convert single loads with the Watts to Amps Calculator and the Amps to Watts Calculator, or solve voltage, current, resistance and power together in the Ohm's Law Calculator.
Frequently asked questions
How do I convert kVA to amps?
For single-phase, multiply the kVA by 1,000 and divide by the voltage. For three-phase, also divide by the square root of three, using the line-to-line voltage.
How many amps is a 50 kVA transformer?
At 400 V three-phase it supplies about 72.17 A per line, and at 480 V about 60.14 A. A 50 kVA single-phase unit at 240 V supplies about 208.33 A.
Why is kVA to amps independent of the power factor?
Apparent power in kVA already counts the full current, including the part that does no work. The power factor only matters when you want the real power in kW.
What is the difference between kVA and kW?
kVA is apparent power, voltage times current. kW is real power, the part that does useful work. Real power equals apparent power times the power factor, so 50 kVA at 0.8 is 40 kW.
Why do generators assume a power factor of 0.8?
Generator makers rate their machines for typical mixed loads with motors, which average around 0.8. A 10 kVA generator is therefore often sold as an 8 kW generator.