kVA (kilovolt-ampere) is the unit of apparent power in an AC circuit. It represents the total power the source must supply, combining real power (kW) that performs useful work and reactive power (kVAR) consumed by inductive or capacitive loads.

What formula is used for single-phase circuits?

For single-phase AC: S(kVA) = V(V) × I(A) / 1000. Multiply the voltage by the current and divide by 1000 to convert volt-amperes to kilovolt-amperes.

What formula is used for three-phase circuits?

For three-phase AC: S(kVA) = √3 × V(V) × I(A) / 1000. The √3 factor (approximately 1.7321) accounts for the three-phase relationship. Enter the line-to-line voltage.

Should I enter line-to-line or line-to-neutral voltage for three-phase?

Enter the line-to-line (phase-to-phase) voltage for three-phase calculations. For example, a 480 V three-phase system uses 480 V, not 277 V. The formula already accounts for this with the √3 factor.

What is the difference between kVA and kW?

kVA is apparent power — the total power drawn from the supply. kW is real power — the portion that performs actual work. They are related by the power factor: kW = kVA × PF. For purely resistive loads the power factor equals 1 and kW equals kVA.

Can I use this calculator for DC circuits?

No. kVA is an AC concept only. DC circuits have no reactive power or phase angle, so apparent power does not apply. For DC, use P(W) = V(V) × I(A) and divide by 1000 to get kilowatts.

Volts to kVA Calculator

Enter voltage (V) and current (A) to calculate apparent power in kilovolt-amperes (kVA) for single-phase or three-phase AC circuits.

Input Values

Circuit Type

Single-Phase Three-Phase

Voltage (V) — line voltage

Current (A)

Result

Enter voltage and current, then click Calculate.

Reference Formulas

Single-Phase

kVA = V × A / 1000

Example: 120 V × 10 A / 1000 = 1.2 kVA

Three-Phase

kVA = √3 × V × A / 1000

Example: 1.7321 × 480 V × 10 A / 1000 = 8.314 kVA

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Summary

This calculator converts voltage in volts (V) and current in amperes (A) to apparent power in kilovolt-amperes (kVA). It supports both single-phase and three-phase AC circuits using standard electrical engineering formulas. Results are useful for sizing transformers, generators, switchgear, and UPS systems.

How it works

Select your circuit type: single-phase AC or three-phase AC.
Enter the voltage in volts (V) — use line-to-line voltage for three-phase.
Enter the current in amperes (A).
Click Calculate to compute the apparent power in kVA.
The result panel shows the kVA value, the formula applied, and a summary table.
Click Reset to clear all fields and start over.

Use cases

Size transformers and generators for residential or commercial installations.
Determine UPS capacity requirements for servers and critical equipment.
Calculate apparent power for three-phase industrial motors and drives.
Specify circuit protection ratings and switchgear ampacity.
Compare single-phase and three-phase power for the same voltage and current.
Estimate panel board capacity when planning electrical service upgrades.
Convert nameplate voltage and current ratings to kVA for equipment procurement.
Verify that existing electrical infrastructure can support new load additions.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu