kVA Calculator — Volts and Amps to kVA | Single-Phase & Three-Phase | kVA to kW Converter

What does kVA mean?

Kilovolt-amps, abbreviated as kVA, is the typical unit of measure for what is called apparent power. Apparent power is the amount of electrical power produced by an electrical system at a particular applied voltage and current. Following Ohm's law, we can obtain the amount of electrical power by multiplying the voltage by the current flowing through any electrical system.

Since we measure voltage in volts and current in amperes, we can express power in units of volt-amperes. Although watts are the standard unit of power, we still use volt-amperes for a particular reason discussed below.

What is the difference between kVA and kW?

The main difference between kilovolt-amperes (kVA) and kilowatts (kW) is the presence of the power factor. The power factor (PF) is the ratio between the real power (measured in watts) and the apparent power (measured in volt-amperes):

Power Factor (PF) = Real Power (kW) / Apparent Power (kVA)

In other words, the power factor determines how much of the apparent power is converted to real (usable) power. Electrical systems such as transformers, generators, pumps, and motors often have an unknown power factor, which is why we rate them in volt-amperes or kilovolt-amperes rather than watts.

How do I calculate kVA?

Use the apparent power formula based on your circuit type:

Single-Phase Circuit

S (kVA) = V × I / 1000

Where V is the voltage in volts and I is the current in amperes.

Three-Phase Circuit

S (kVA) = √3 × V × I / 1000 ≈ 1.732 × V × I / 1000

kVA to kW Conversion

P (kW) = S (kVA) × PF

Where PF is the power factor (a dimensionless number between 0 and 1).

kVA to Watts

W = kVA × 1000 × PF

kVA to Horsepower (American units)

HP = kW / 0.7457

kVA to BTU/hr (American units)

BTU/hr = kW × 3412.142

Sample Volts and Amps to kVA Calculation

Suppose you have a single-phase circuit with 120 V and 10 A, and a power factor of 0.85:

S = 120 × 10 / 1000 = 1.2 kVA
P = 1.2 × 0.85 = 1.02 kW
W = 1020 W
HP = 1.02 / 0.7457 ≈ 1.368 HP
BTU/hr = 1.02 × 3412.142 ≈ 3480.4 BTU/hr

For a three-phase circuit with 480 V, 20 A, and PF = 0.9:

S = 1.732 × 480 × 20 / 1000 ≈ 16.628 kVA
P = 16.628 × 0.9 ≈ 14.965 kW

FAQs

What is a good power factor?

A power factor of 1.0 (unity) is ideal — it means all the apparent power is being converted to real work. In practice, most industrial loads have a power factor between 0.8 and 0.95. Resistive loads (heaters, incandescent lights) have a PF close to 1; inductive loads (motors, transformers) typically have a PF of 0.7–0.9.

Why does the power factor matter?

A low power factor means you need more current (and therefore larger cables and equipment) to deliver the same real power. Utilities often charge commercial customers extra for poor power factor because it increases the load on the grid.

What is the difference between single-phase and three-phase?

Single-phase power uses two wires (one live, one neutral) and is typical in residential applications (120 V in the US, 230 V in Europe). Three-phase power uses three live conductors and is common in industrial and commercial settings (480 V in the US, 400 V in Europe). Three-phase systems are more efficient for high-power loads.

How do I convert kVA to amps?

Rearrange the kVA formula:

Single-phase: I (A) = S (kVA) × 1000 / V
Three-phase:  I (A) = S (kVA) × 1000 / (√3 × V)

Want to learn more?

This calculator is part of our Electromagnetism collection. You may also find useful our Power Factor Calculator, Watt Calculator, and Electrical Power Calculator.