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kVA Calculator (Amps, kW and kVA for Single & Three-Phase)

Convert between kVA, amps and kW for single-phase and three-phase systems. Built for sizing transformers, generators and services.

kVA
V
0.1 - 1.0

kVA and Amps do not depend on PF. PF only converts between kVA and kW.

kVA Conversion Results

Apparent Power (S)
100 kVA

Three-phase at 480 V

Line Current (I)
120.28 A
Real Power (P)
80 kW

At power factor 0.8

Step-by-Step Engineering Calculation

  1. 1Apparent power: S=100 kVAS = 100\text{ kVA} at 480 V480\text{ V} (3-Phase)
  2. 2Current: I=100×10003×480=120.28 AI = \frac{100 \times 1000}{\sqrt{3} \times 480} = \mathbf{120.28\text{ A}}
  3. 3Real power at PF 0.8: P=100×0.8=80.00 kWP = 100 \times 0.8 = \mathbf{80.00\text{ kW}}

Formula & Theory

S (kVA) = (√3 × V × I) / 1000 (3-Phase) | S (kVA) = (V × I) / 1000 (1-Phase) | P (kW) = S × PF

Apparent power in kVA is what transformers, generators and UPS units are rated in. Three-phase kVA uses the line-to-line voltage with the √3 factor; real power in kW follows from the power factor.

Variable Definitions
S:
Apparent Power (kVA) – Total power the source must deliver, including reactive power
P:
Real Power (kW) – Power that does actual work, equal to kVA × PF
V:
Voltage (Volts (V)) – Line-to-line voltage for three-phase, line voltage for single-phase
I:
Current (Amperes (A)) – Line current drawn at the stated voltage
PF:
Power Factor (Ratio (0 to 1)) – Only needed to convert between kVA and kW

Worked Engineering Example

100 kVA Transformer at 480 V

A 100 kVA three-phase transformer secondary at 480 V, feeding a load with 0.8 power factor.

Inputs:
  • Apparent Power: 100 kVA
  • Voltage: 480 V
  • Power Factor: 0.8
Result: Current = 120.28 A, Real Power = 80.00 kW

Key Assumptions

  • •Balanced three-phase load (equal current on all three phases).
  • •Voltage entered for three-phase is the line-to-line value.
  • •Power factor is constant at the operating point.

Limitations & Safety Scope

  • •Unbalanced loads need per-phase calculation; the largest phase current governs equipment sizing.
  • •Transformer kVA ratings also carry temperature-rise and altitude limits this calculator does not model.

Frequently Asked Questions

How many amps is 100 kVA at 480 V three-phase?

I = (100 × 1000) / (√3 × 480) = 120.28 A. The same transformer at 208 V would deliver 277.6 A, which is why higher voltages are used for large loads.

What is the difference between kVA and kW?

kW is real power that does work. kVA is apparent power, which adds the reactive power motors and transformers circulate. They are equal only at a power factor of 1.0; at PF 0.8 a load needs 1.25 kVA for every 1 kW.

How do I size a transformer from a kW load?

Divide the kW load by the power factor to get kVA, then choose the next standard transformer size above that figure and add headroom for future load growth.

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Educational & Reference Notice: This calculator provides technical estimates based on standard physical formulas. Actual electrical installation, protective device sizing, and conductor selection must be verified against the applicable electrical code (NEC, IEC, CEC) by a licensed electrician or qualified professional engineer.