kVA to Amps Calculator
Convert kilovolt-amps to amperes for single-phase and three-phase circuits. Enter the kVA rating and voltage to find full-load current — the number you need to size breakers, conductors, and switchgear for a transformer or generator.
How to Convert kVA to Amps
Multiply kVA by 1,000 to get volt-amps, then divide by the voltage.For three-phase circuits, divide by 1.732 (√3) times the line-to-line voltage, because the load is shared across three conductors.
Single-phase: Amps = kVA × 1,000 ÷ Volts
Three-phase: Amps = kVA × 1,000 ÷ (1.732 × Volts)
Worked example (three-phase): A 50 kVA transformer at 480V three-phase delivers 50,000 ÷ (1.732 × 480) = 50,000 ÷ 831.4 = 60.1 amps. The same 50 kVA at 208V delivers 138.8 amps — lower voltage means higher current for the same power.
Worked example (single-phase): A 25 kVA single-phase transformer at 240V delivers 25,000 ÷ 240 = 104.2 amps.
Amps to kVA (reverse conversion)
To go from amps to kVA, reverse the formula: kVA = Volts × Amps ÷ 1,000 for single-phase, or kVA = 1.732 × Volts × Amps ÷ 1,000 for three-phase. For example, a 100-amp three-phase load at 480V is 1.732 × 480 × 100 ÷ 1,000 = 83.1 kVA. Our kVA calculatorhandles this direction — enter volts and amps to get kVA.
Transformer kVA to Amps Chart (Three-Phase)
Full-load amps for standard three-phase transformer sizes at 208V and 480V:
| Transformer Size | Amps @ 208V (3Φ) | Amps @ 480V (3Φ) |
|---|---|---|
| 15 kVA | 41.6 A | 18.0 A |
| 30 kVA | 83.3 A | 36.1 A |
| 45 kVA | 124.9 A | 54.1 A |
| 75 kVA | 208.2 A | 90.2 A |
| 112.5 kVA | 312.3 A | 135.3 A |
| 150 kVA | 416.4 A | 180.4 A |
| 225 kVA | 624.5 A | 270.6 A |
| 300 kVA | 832.7 A | 360.8 A |
| 500 kVA | 1387.9 A | 601.4 A |
These are full-load amperages at rated voltage. When sizing overcurrent protection for transformers, apply the percentages in NEC 450.3 rather than using full-load amps directly. For picking a transformer size from a known load, see the transformer sizing calculator.
Frequently Asked Questions
How many amps is 75 kVA?
A 75 kVA three-phase transformer delivers 208.2 amps at 208V (75,000 ÷ (1.732 × 208)) and 90.2 amps at 480V (75,000 ÷ (1.732 × 480)). On a 240V single-phase system, 75 kVA is 312.5 amps (75,000 ÷ 240). The same kVA rating produces very different amperages depending on voltage and phase.
How do you convert kVA to amps?
Multiply kVA by 1,000 to get volt-amps, then divide by the voltage. Single-phase: Amps = kVA × 1,000 ÷ Volts. Three-phase: Amps = kVA × 1,000 ÷ (1.732 × Volts). For example, 50 kVA at 480V three-phase is 50,000 ÷ (1.732 × 480) = 60.1 amps.
How do you convert amps to kVA?
Reverse the formula: multiply volts by amps and divide by 1,000. Single-phase: kVA = Volts × Amps ÷ 1,000. Three-phase: kVA = 1.732 × Volts × Amps ÷ 1,000. For example, a 100-amp load at 480V three-phase is 1.732 × 480 × 100 ÷ 1,000 = 83.1 kVA.
How many amps is a 50 kVA transformer good for?
At 208V three-phase, a 50 kVA transformer delivers 138.8 full-load amps. At 480V three-phase, it delivers 60.1 amps. At 240V single-phase, it delivers 208.3 amps. Full-load amps is the continuous current the transformer can supply at its rated voltage without exceeding its temperature rating.
Why is 1.732 used in three-phase kVA calculations?
1.732 is the square root of 3. In a three-phase system, power is delivered over three conductors whose voltages are 120 degrees apart, and the math of combining them introduces a factor of √3 between line-to-line voltage and the per-phase values. That is why three-phase power = √3 × line voltage × line current.
Does power factor affect the kVA to amps conversion?
No. kVA is apparent power — volts times amps by definition — so converting kVA to amps needs only the voltage and phase configuration. Power factor only enters the picture when converting between kVA and kW (real power): kW = kVA × PF. That is also why transformer ratings are given in kVA rather than kW.
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