Amps to kW calculator
Enter current, voltage and power factor to get real power in kW.
VC-2 converterA → kW
Supply
A
V
1 for heaters; ~0.85 motors
Power74.82kW
kW = √3 × V × I × PF ÷ 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 | 240 V 1-ph | 208 V 3-ph | 480 V 3-ph |
|---|---|---|---|
| 10 A | 2.4 | 3.6 | 8.31 |
| 20 A | 4.8 | 7.21 | 16.63 |
| 30 A | 7.2 | 10.81 | 24.94 |
| 50 A | 12 | 18.01 | 41.57 |
| 60 A | 14.4 | 21.62 | 49.88 |
| 100 A | 24 | 36.03 | 83.14 |
| 150 A | 36 | 54.04 | 124.7 |
| 200 A | 48 | 72.05 | 166.3 |
| 400 A | 96 | 144.1 | 332.6 |
kW at power factor 1.
The formulas
DC: P = V × I, so I = P ÷ V
AC single-phase: P = V × I × PF, so I = P ÷ (V × PF)
AC three-phase: P = 1.732 × VLL × I × PF, so I = P ÷ (1.732 × VLL × PF)
PF is power factor, between 0 and 1. Resistive loads (heaters, incandescent lamps, water heaters) are 1. Motors, compressors and power supplies are lower, which means they draw more current for the same watts.
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 many kW is 100 amps?
24 kW at 240 V single-phase (PF 1). On 208 V three-phase at PF 1 it is 1.732 × 208 × 100 ÷ 1000 = 36 kW.
How many kW is a 200 amp service?
A 200 A, 240 V residential service can deliver 48 kW at full rating. The usable continuous load is lower; a service load calculation per NEC Article 220 decides what it can actually support.