What is the Amps to kVA Calculator?
This calculator converts electric current (amps) and voltage into apparent power, expressed in kilovolt-amperes (kVA). Apparent power is the product of the RMS voltage and RMS current in a circuit, and it is the figure used to size transformers, generators, UPS systems and cabling. Unlike real power (kW), apparent power does not depend on the power factor, which makes it ideal for equipment ratings.
How to use it
Select whether your system is single phase or three phase, then enter the voltage and current. For single phase, use the line voltage (for example 230 V or 120 V). For three phase, enter the line-to-line voltage (for example 400 V or 480 V) and the line current. The result is shown in kVA and also in volt-amperes (VA).
The formula explained
For a single phase circuit, apparent power is simply the voltage times the current divided by 1000 to convert VA to kVA:
$$\text{kVA} = \frac{V \times I}{1000}$$For a balanced three phase system, the line quantities are related by the square root of three, so
$$\text{kVA} = \frac{1.732 \times V \times I}{1000}$$The factor of root three comes from the 120-degree phase displacement between the three phases.
Worked example
A three phase motor draws 50 A at 400 V line-to-line. Apparent power =
$$1.732 \times 400 \times \frac{50}{1000} = 34.64 \text{ kVA}$$The same 50 A at 400 V on a single phase basis would be
$$400 \times \frac{50}{1000} = 20 \text{ kVA}$$
FAQ
Is kVA the same as kW? No. kVA is apparent power and kW is real power. They are related by the power factor: \(\text{kW} = \text{kVA} \times \text{power factor}\).
Which voltage do I use for three phase? Use the line-to-line (phase-to-phase) voltage, such as 400 V or 480 V.
Why divide by 1000? Volts times amps gives volt-amperes (VA); dividing by 1000 converts to kilovolt-amperes (kVA).
