Amps to kVA calculator
Enter current and voltage to get apparent power. Use this to size a transformer, UPS or generator for a known current draw.
VC-2 converterA → kVA
Supply
A
V
Apparent power83.14kVA
kVA = √3 × V × I ÷ 1000Breaker: 100 A non-continuous · 125 A if it runs 3 h+
Breaker figures are the next standard size from NEC 240.6(A), with 125% for continuous loads (210.20(A)). The wire must be rated for the breaker, and motors and HVAC follow different rules. See the breaker size calculator.
Quick reference
| Amps | 120 V | 240 V | 208 V 3-ph | 480 V 3-ph |
|---|---|---|---|---|
| 10 A | 1.2 | 2.4 | 3.6 | 8.31 |
| 20 A | 2.4 | 4.8 | 7.21 | 16.63 |
| 30 A | 3.6 | 7.2 | 10.81 | 24.94 |
| 50 A | 6 | 12 | 18.01 | 41.57 |
| 100 A | 12 | 24 | 36.03 | 83.14 |
| 200 A | 24 | 48 | 72.05 | 166.3 |
| 400 A | 48 | 96 | 144.1 | 332.6 |
kVA (apparent power).
The formulas
Single-phase: I = kVA × 1000 ÷ V and kVA = V × I ÷ 1000
Three-phase: I = kVA × 1000 ÷ (1.732 × VLL) and kVA = 1.732 × VLL × I ÷ 1000
kVA is apparent power. It is what transformers, generators and UPS units are rated in, because their heating depends on current whatever the power factor. To get real power: kW = kVA × PF.
Using the result safely
- Nameplate current beats a calculation. If the equipment lists amps, use that figure.
- For a load that runs 3 hours or more (EV charger, water heater, space heater), the NEC sizes conductors and breakers at 125% of the load.
- To pick the conductor for the current you found, go to the wire size calculator; for long runs check the voltage drop.
Questions people ask
How do I convert amps to VA?
Single-phase: VA = V × A. Three-phase: VA = √3 × V × A. Divide by 1,000 for kVA.
How many kVA is 100 amps?
24 kVA at 240 V single-phase; 36 kVA at 208 V three-phase; 83.1 kVA at 480 V three-phase.