Amps to kVA Calculator - Single-Phase and Three-Phase

Agarapu Ramesh — Editor and content reviewer
Editorially reviewed Reviewed by Agarapu Ramesh, science educator (chemistry). LinkedIn
Last reviewed: May 2026 | Standard electrical engineering formulas

kVA is apparent power. If you know amps and voltage, you can size the transformer, UPS or generator without guessing at real watts. Single-phase kVA = volts x amps / 1000. Three-phase kVA = sqrt(3) x line volts x line amps / 1000.

Formula at a glance

  • single-phase: kVA = V x A / 1000
  • three-phase: kVA = 1.732 x V x A / 1000
  • DC apparent power is usually treated as W, not kVA

Field note: If the equipment nameplate gives both kVA and kW, believe the nameplate. The calculator is for planning and cross-checking, not arguing with manufacturer data.

⚡

Calculator Tool

Convert current to apparent power

A
V
Result
—

Formulas

AC 1-PhasekVA = (I×V) ÷ 1000
AC 3-PhasekVA = (√3×I×V) ÷ 1000

Related Calculators

kVA to Amps kVA to kW kW to kVA

How to use the Amps to kVA Calculator

Use this as a fast electrical check, then compare the result with the nameplate, measured voltage and power factor. The formula is clean. Real panels, motors and UPS loads usually have one extra wrinkle.

Worked example

Example: 40 A at 240 V single-phase is 9.6 kVA. The same 40 A on a 415 V three-phase system is 28.75 kVA.

Practical checks before you trust the number

  • Use line-to-line voltage for three-phase. Using 240 V instead of 415 V is a very common bad day.
  • kVA ignores power factor. That is fine for transformer and UPS capacity, but it is not the same as kW.
  • Leave margin for starting current if the load includes motors or compressors.

Common mistake

If the equipment nameplate gives both kVA and kW, believe the nameplate. The calculator is for planning and cross-checking, not arguing with manufacturer data.

Sources and references

Related calculators

Frequently Asked Questions

For single-phase, use volts x amps / 1000. For 3-phase, use 1.732 x line volts x amps / 1000.

No. kVA is apparent power, so PF is not part of this conversion.

Enter line-to-line voltage, not line-to-neutral voltage.

Yes. Multiply kVA by power factor to estimate kW.