Electrical Calc Lab

kVA Calculator

Calculate kVA, amps or kW from voltage, current and power factor for single-phase and balanced three-phase AC systems.

What do you want to calculate?
Phase

Use this calculator as a calculation aid only. Verify results and applicable requirements before design or installation.

kVA vs kW

kVA is apparent power in an AC system. It represents the combination of voltage and current before power factor is used to determine how much of that apparent power becomes real working power.

kW is real power. The relationship between the two is power factor:

  • kVA = kW ÷ PF
  • kW = kVA × PF

For example, an 80 kW load at a power factor of 0.80 is 100 kVA.

Power factor is required when converting between kW and kVA. It is not required when converting directly between kVA and current because kVA already represents apparent power derived from voltage and current.

Single-phase vs three-phase kVA

Single-phase and balanced three-phase systems use different relationships between apparent power, voltage and current.

For single-phase AC:

kVA = V × I ÷ 1000

For balanced three-phase AC:

kVA = √3 × VLL × I ÷ 1000

In three-phase mode, this calculator uses RMS line-to-line voltage (VLL) and RMS line current. The √3 factor comes from the relationship between phase quantities in a balanced three-phase system.

Use the line-to-line voltage for the three-phase input. For example, enter 208 for a 208Y/120 V system or 480 for a 480Y/277 V system.

The same kVA and voltage can produce a different current depending on whether the system is single-phase or three-phase, so this calculator does not guess the phase.

Worked examples

These examples use the same formulas and assumptions as the calculator. They are calculation examples, not equipment-sizing or code-compliance recommendations.

Example 1 — 100 A at 415 V, balanced three-phase

Inputs:

  • Phase: three-phase
  • Line-to-line voltage: 415 V
  • Line current: 100 A

Result:

71.88 kVA

Formula:

kVA = √3 × VLL × I ÷ 1000

Substitution:

√3 × 415 × 100 ÷ 1000 = 71.88 kVA

Example 2 — 100 kVA at 415 V, balanced three-phase

Inputs:

  • Apparent power: 100 kVA
  • Phase: three-phase
  • Line-to-line voltage: 415 V

Result:

139.12 A

Formula:

I = kVA × 1000 ÷ (√3 × VLL)

Substitution:

100 × 1000 ÷ (√3 × 415) = 139.12 A

Example 3 — 10 kVA at 230 V, single-phase

Inputs:

  • Apparent power: 10 kVA
  • Phase: single-phase
  • Voltage: 230 V

Result:

43.48 A

Formula:

I = kVA × 1000 ÷ V

Substitution:

10 × 1000 ÷ 230 = 43.48 A

Example 4 — 10 kVA at 230 V, balanced three-phase

Inputs:

  • Apparent power: 10 kVA
  • Phase: three-phase
  • Line-to-line voltage: 230 V

Result:

25.10 A

Formula:

I = kVA × 1000 ÷ (√3 × VLL)

Substitution:

10 × 1000 ÷ (√3 × 230) = 25.10 A

Example 5 — 10 kVA at 208 V, balanced three-phase

Inputs:

  • Apparent power: 10 kVA
  • Phase: three-phase
  • Line-to-line voltage: 208 V

Result:

27.76 A

Formula:

I = kVA × 1000 ÷ (√3 × VLL)

Substitution:

10 × 1000 ÷ (√3 × 208) = 27.76 A

Example 6 — 80 kW at PF 0.80

Inputs:

  • Real power: 80 kW
  • Power factor: 0.80

Result:

100.00 kVA

Formula:

kVA = kW ÷ PF

Example 7 — 100 kVA at PF 0.80

Inputs:

  • Apparent power: 100 kVA
  • Power factor: 0.80

Result:

80.00 kW

Formula:

kW = kVA × PF

How to use the kVA calculator

  1. Choose what you want to calculate: kVA from volts and amps, amps from kVA and volts, kVA from kW and power factor, or kW from kVA and power factor.
  2. For direct voltage/current calculations, choose Single-phase or Three-phase. No phase is assumed for you.
  3. Enter the required values. Power factor is entered as a decimal greater than 0 and up to 1, such as 0.80 or 0.95.
  4. Select Calculate.
  5. Review the result, formula, substituted calculation and assumptions shown by the calculator.

Plain decimal values and scientific notation such as 1e3 are accepted. Commas, percent signs and non-decimal number formats are not accepted.

Frequently asked questions

How do I calculate kVA from amps and volts?

For single-phase AC, multiply volts by amps and divide by 1000. For balanced three-phase AC, multiply line-to-line volts by line current and by √3, then divide by 1000.

Is kVA the same as kW?

Not necessarily. kVA is apparent power and kW is real power. For the positive power-factor magnitude used by this calculator, kW = kVA × PF. They are numerically equal when power factor is 1.

Why does the kVA-to-amps calculation not use power factor?

Because kVA is already apparent power. Current can be calculated directly from kVA, voltage and phase. Power factor is needed when converting between real power in kW and apparent power in kVA.

What voltage should I use for a three-phase calculation?

Use RMS line-to-line voltage. For example, use 208 V for a 208Y/120 V system and 480 V for a 480Y/277 V system.

Why do I have to select single-phase or three-phase?

The formulas are different. For example, 10 kVA at 230 V is about 43.48 A single-phase but about 25.10 A in a balanced three-phase system using 230 V line-to-line.

Can I enter 80 for an 80% power factor?

No. Enter power factor as a decimal, such as 0.80. The calculator does not convert 80 or 80% into 0.80.