What is the kVA?
Choose single-phase or three-phase, then enter the voltage and the current to get kVA, or the kVA to get the current. Add the power factor to see the real power in kW.
- Apparent power (kVA)
- 12
240 V at 50 A is 12 kVA (9.6 kW at the power factor given).
- Current (A)
- 50
- Real power (kW)
- 9.6
- Reactive power (kVAR)
- 7.2
- Apparent power (VA)
- 12,000
Apparent power (kVA): 12. 240 V at 50 A is 12 kVA (9.6 kW at the power factor given).
How to calculate
Works out apparent power in kVA from volts and amps for single-phase or three-phase circuits, or the current from kVA and volts, with real power in kW from the power factor.
Example with the default inputs (Supply Single-phase, Find kVA, Voltage 240 V, Current 50 A, Power factor 0.8): 240 V at 50 A is 12 kVA (9.6 kW at the power factor given).
Method: Single-phase: kVA = V × I ÷ 1,000, I = kVA × 1,000 ÷ V. Three-phase: kVA = √3 × V × I ÷ 1,000, I = kVA × 1,000 ÷ (√3 × V). kW = kVA × pf; kVAR = kVA × √(1 − pf²).
- RMS values on a sinusoidal supply; for three-phase, a balanced load with the line-to-line voltage and the line current.
- The power factor only changes kW and kVAR; kVA and amps do not depend on it.
Worked examples
Each example is checked against the calculator on every build.
- Supply Single-phase, Find kVA, Voltage 240 V, Current 50, Power factor 0.8 gives Apparent power (kVA) 12, Real power (kW) 9.6, Reactive power (kVAR) 7.2, Apparent power (VA) 12,000.Source: OpenStax, University Physics Volume 2, §15.4 Power in an AC Circuit (average power = I_rms V_rms cos φ; power factor cos φ), https://openstax.org/books/university-physics-volume-2/pages/15-4-power-in-an-ac-circuit (retrieved 2026-10-05)
- Supply Three-phase, Find kVA, Voltage 480 V, Current 100, Power factor 1 gives Apparent power (kVA) 83.138439, Real power (kW) 83.138439, Reactive power (kVAR) 0.Source: Wikipedia, "Three-phase electric power" (balanced load: apparent power = √3 × line voltage × line current), https://en.wikipedia.org/wiki/Three-phase_electric_power (retrieved 2026-10-05)
- Supply Three-phase, Find Amps, Voltage 208 V, Apparent power (kVA) 75, Power factor 0.9 gives Current 208.179184, Real power (kW) 67.5.Source: Wikipedia, "Three-phase electric power" (balanced load: apparent power = √3 × line voltage × line current), https://en.wikipedia.org/wiki/Three-phase_electric_power (retrieved 2026-10-05)
- Supply Single-phase, Find Amps, Voltage 120 V, Apparent power (kVA) 1.8, Power factor 1 gives Current 15.Source: OpenStax, University Physics Volume 2, §15.4 Power in an AC Circuit (average power = I_rms V_rms cos φ; power factor cos φ), https://openstax.org/books/university-physics-volume-2/pages/15-4-power-in-an-ac-circuit (retrieved 2026-10-05)
How it works
Apparent power S is volts times amps. With V the RMS voltage (line-to-line for three-phase) and I the RMS current in a line:
- Single-phase: S (kVA) = V × I ÷ 1,000, and I = S × 1,000 ÷ V
- Balanced three-phase: S (kVA) = √3 × V × I ÷ 1,000, and I = S × 1,000 ÷ (√3 × V)
With the power factor pf (from 0 to 1):
- Real power P (kW) = S × pf
- Reactive power Q (kVAR) = S × √(1 − pf²)
Rules
- Voltage from 1 mV to 1,000 kV; current from 1 µA to 1,000,000 A; apparent power from 0.000001 to 10,000,000 kVA; power factor from 0 to 1.
- Single-phase steps are exact on the numbers as typed; three-phase steps use √3 as a float. Values are shown to 6 significant figures.
Worked examples by hand
240 V single-phase, 50 A, pf 0.8. S = 240 × 50 ÷ 1,000 = 12 kVA (12,000 VA). P = 12 × 0.8 = 9.6 kW. Q = 12 × √(1 − 0.64) = 12 × 0.6 = 7.2 kVAR.
480 V three-phase, 100 A, pf 1. S = 1.7320508 × 480 × 100 ÷ 1,000 = 83.1384 kVA; P = 83.1384 kW and Q = 0.
75 kVA three-phase at 208 V, pf 0.9. I = 75,000 ÷ (1.7320508 × 208) = 75,000 ÷ 360.2666 = 208.179 A. P = 75 × 0.9 = 67.5 kW.
1.8 kVA single-phase at 120 V. I = 1,800 ÷ 120 = 15 A.
Other questions people ask
How do I calculate kVA?
For single-phase, multiply volts by amps and divide by 1,000: 240 V × 50 A = 12,000 VA = 12 kVA. For balanced three-phase, multiply by √3 (about 1.732) as well, using the line-to-line voltage: √3 × 480 V × 100 A ÷ 1,000 = 83.1 kVA.
How do I convert kVA to amps?
Single-phase: amps = kVA × 1,000 ÷ volts, so 1.8 kVA at 120 V is 15 A. Three-phase: amps = kVA × 1,000 ÷ (√3 × volts), so a 75 kVA load at 208 V draws about 208.2 A per line.
What is the difference between kVA and kW?
kVA is apparent power: volts times amps. kW is real power, the part that does work, and equals kVA × power factor. A motor drawing 12 kVA at a power factor of 0.8 uses 9.6 kW. For a heater, with a power factor of 1, the two are the same.
What is kVAR?
Reactive power, in kilovolt-amperes reactive. It flows back and forth between the supply and coils or capacitors and does no work. kW, kVAR and kVA form a right triangle: kVA² = kW² + kVAR².
Why are transformers and generators rated in kVA?
Their heating depends on the current, and the current depends on kVA, not on the power factor of the load. A kVA rating holds for any load; the kW they can deliver depends on the power factor of what is connected.
Which voltage do I use for three-phase?
The line-to-line voltage, such as 208 V, 400 V or 480 V, and the current in one line. The √3 in the formula assumes a balanced load, with the same current in each line.