Convert kW to amps
Work out the current from the power, or the power from the current, for DC, single-phase and three-phase circuits. With the formulas, worked examples and a table of common values.
Calculator
Formulas
P is the power in kW, V the voltage in volts, I the current in amps, cos φ the power factor and η the efficiency.
| System | kW to amps | Amps to kW |
|---|---|---|
| DC | I = P × 1000 / V | P = V × I / 1000 |
| Single-phase | I = P × 1000 / (V × cos φ) | P = V × I × cos φ / 1000 |
| Three-phase | I = P × 1000 / (√3 × V × cos φ) | P = √3 × V × I × cos φ / 1000 |
If P is a motor's mechanical power, also divide by the efficiency: in three-phase, I = P × 1000 / (√3 × V × cos φ × η). √3 is approximately 1.732.
Worked examples
- 7.5 kW motor at 400 V three-phase, cos φ 0.85, efficiency 90 %.
I = 7500 / (1.732 × 400 × 0.85 × 0.90) = 14.15 A - 2 kW heater at 230 V single-phase (cos φ 1).
I = 2000 / 230 = 8.70 A - Power of a 32 A three-phase line at 400 V with cos φ 0.9.
P = 1.732 × 400 × 32 × 0.9 / 1000 = 19.95 kW
kW to amps table
Current in amps for loads of common power ratings:
| Power (kW) | Single-phase 230 V cos φ = 1 | Three-phase 400 V cos φ = 1 | Three-phase 400 V cos φ = 0.85 |
|---|---|---|---|
| 0.37 | 1.61 | 0.53 | 0.63 |
| 0.75 | 3.26 | 1.08 | 1.27 |
| 1.1 | 4.78 | 1.59 | 1.87 |
| 1.5 | 6.52 | 2.17 | 2.55 |
| 2.2 | 9.57 | 3.18 | 3.74 |
| 3 | 13.04 | 4.33 | 5.09 |
| 4 | 17.39 | 5.77 | 6.79 |
| 5.5 | 23.91 | 7.94 | 9.34 |
| 7.5 | 32.61 | 10.83 | 12.74 |
| 11 | 47.83 | 15.88 | 18.68 |
| 15 | 65.22 | 21.65 | 25.47 |
| 18.5 | 80.43 | 26.70 | 31.41 |
| 22 | 95.65 | 31.75 | 37.36 |
| 30 | 130.43 | 43.30 | 50.94 |
| 37 | 160.87 | 53.40 | 62.83 |
| 45 | 195.65 | 64.95 | 76.41 |
| 55 | 239.13 | 79.39 | 93.39 |
| 75 | 326.09 | 108.25 | 127.36 |
| 90 | 391.30 | 129.90 | 152.83 |
| 110 | 478.26 | 158.77 | 186.79 |
The values are the current of a load with that electrical power. A motor's rated current is somewhat higher, because its stated power is the mechanical output: always check its rating plate.
Common questions
How many amps is 1 kW?
It depends on the voltage and the system: at 230 V single-phase with cos φ 1 it is 4.35 A; at 400 V three-phase with cos φ 1 it is 1.44 A.
What is the power factor for?
In AC circuits, motors and coils also draw reactive power, so the current is higher than the active power alone suggests. The cos φ accounts for that difference; for purely resistive loads it is 1.
Which voltage do I use for three-phase?
The line-to-line voltage (for example 400 V in Europe), not the line-to-neutral voltage (230 V).
How do I convert kVA to amps?
With the same formula and cos φ = 1: kVA is apparent power and already includes the power factor.
Can I use it to choose the cable or the protection?
It gives the operating current, which is the starting point. Cable cross-section and protection also depend on the installation method, temperature, length and local regulations.