ElectroHub

kVA to Amps Calculator & Formula

Transformers, generator sets and UPS units are rated in kVA rather than kW because what limits them is current and voltage, not the power factor of whatever gets plugged in. Converting between kVA and amps is the first step in sizing anything downstream.

kVA ↔ amps

Transformers, DG sets and UPS units are rated in kVA because they are limited by current and voltage, not by what power factor the load happens to have. This converts either way, at line voltage.

Line current
Apparent power
  1. 1.FormulaI = kVA × 1000 / (√3 × V)SubstituteI = 100 × 1000 / (1.732 × 415)ResultI = 139.12 A
  2. 2.The √3 is the whole difference between line and phase quantities. Dropping it over-states the current by 73 %, which is the single most common three-phase mistake.
Common trap: kVA is not kW. A 100 kVA set at 0.8 power factor delivers only 80 kW — but it still carries the full 139 A at 415 V, and it is the current that sizes the cable.

The formula

I = kVA × 1000 / (√3 × V) [three phase] | I = kVA × 1000 / V [single phase]

kVA
apparent power rating
V
line voltage
√3
1.732 — present for three phase only

Worked example

A 100 kVA transformer on a 415 V three-phase system.

  1. I = 100 × 1000 / (1.732 × 415)
  2. I = 100000 / 718.8
  3. I = 139.12 A

139.12 A per line. Dropping the √3 would give 241 A — the classic three-phase mistake.

Where you'll use it

Sizing the cable and protection for a transformer or DG set, and checking whether an existing installation can take a new load. Note the current is set by kVA, not kW: a 100 kVA set at 0.8 power factor delivers 80 kW but still carries the full 139 A.

The laws behind it

Parts this applies to

Resistor (fixed)Potentiometer / Rheostat / TrimmerResistor Array / NetworkThermistor (NTC / PTC)Varistor / MOVSupercapacitorLED (light-emitting diode)MOSFET

Related calculators

Motor Full Load Current CalculatorI = kW × 1000 / (√3 × V × η × cos φ) [three phase]Cable Size CalculatorI_z = I_table × k_ambient × k_grouping3 Phase Power Calculator & FormulaS = √3 × V_L × I_LPower Triangle CalculatorS² = P² + Q²