kW to Amps Calculator
Single-phase, three-phase or DC — with power factor and efficiency
Convert kW, watts or horsepower to amps, or amps back to kW. Single-phase: I = P ÷ (V × PF). Three-phase: I = P ÷ (√3 × V × PF). Size the wire next with the wire gauge calculator.
Power & Current
For three-phase, enter the line-to-line voltage (208V, 400V, 480V).
Heaters 1.0 · motors 0.8–0.9
Use 85–95% if the kW is a motor's rated output
kW to amps chart (A, PF 1.0)
| Power | 120V 1-phase | 240V 1-phase | 208V 3-phase | 480V 3-phase |
|---|---|---|---|---|
| 0.5 kW | 4.17 | 2.08 | 1.39 | 0.60 |
| 0.75 kW | 6.25 | 3.12 | 2.08 | 0.90 |
| 1 kW | 8.33 | 4.17 | 2.78 | 1.20 |
| 1.5 kW | 12.50 | 6.25 | 4.16 | 1.80 |
| 2 kW | 16.67 | 8.33 | 5.55 | 2.41 |
| 2.2 kW | 18.33 | 9.17 | 6.11 | 2.65 |
| 3 kW | 25.00 | 12.50 | 8.33 | 3.61 |
| 3.7 kW | 30.83 | 15.42 | 10.27 | 4.45 |
| 5 kW | 41.67 | 20.83 | 13.88 | 6.01 |
| 5.5 kW | 45.83 | 22.92 | 15.27 | 6.62 |
| 7.5 kW | 62.50 | 31.25 | 20.82 | 9.02 |
| 10 kW | 83.33 | 41.67 | 27.76 | 12.03 |
| 11 kW | 91.67 | 45.83 | 30.53 | 13.23 |
| 15 kW | 125.00 | 62.50 | 41.64 | 18.04 |
| 18.5 kW | 154.17 | 77.08 | 51.35 | 22.25 |
| 22 kW | 183.33 | 91.67 | 61.07 | 26.46 |
| 30 kW | 250.00 | 125.00 | 83.27 | 36.08 |
| 37 kW | 308.33 | 154.17 | 102.70 | 44.50 |
| 45 kW | 375.00 | 187.50 | 124.91 | 54.13 |
| 55 kW | 458.33 | 229.17 | 152.66 | 66.15 |
| 75 kW | 625.00 | 312.50 | 208.18 | 90.21 |
| 100 kW | 833.33 | 416.67 | 277.57 | 120.28 |
Unity power factor and 100% efficiency. For PF 0.8, divide the value by 0.8. 1 HP = 0.7457 kW.
Formulas
| System | Power → current | Current → power |
|---|---|---|
| DC | I = P ÷ V | P = V × I |
| Single-phase AC | I = P ÷ (V × PF) | P = V × I × PF |
| Three-phase AC | I = P ÷ (√3 × V × PF) | P = √3 × V × I × PF |
P is real power in watts, PF the power factor, √3 ≈ 1.732. For output ratings, also divide by efficiency η. Apparent power kVA = (√3 ×) V × I ÷ 1,000, and kW = kVA × PF.
FAQ
How many amps is 1 kW?
At unity power factor, 1 kW draws 8.33 A at 120V, 4.17 A at 240V, and 1.20 A on a 480V three-phase supply.
How do I calculate three-phase motor amps?
I = output (W) ÷ (√3 × V × PF × efficiency). A 10 kW motor on 480V with PF 0.85 and 90% efficiency draws about 10,000 ÷ (1.732 × 480 × 0.85 × 0.9) ≈ 15.72 A. Always check the nameplate full-load amps.
Why does three-phase use √3?
Line-to-line voltage is √3 times the phase voltage, so total three-phase power written with line voltage and line current is P = √3 × V × I × PF.
What is the difference between kW and kVA?
kVA is apparent power (volts × amps); kW is real power that does work. kW = kVA × power factor, so a lower power factor means more current for the same kW. Transformers and generators are rated in kVA.
How many kW can a 30 amp breaker handle?
At unity power factor: 30 × 240 = 7.2 kW single-phase, or √3 × 480 × 30 ≈ 24.9 kW three-phase. For continuous loads, leave headroom below the breaker rating as your electrical code requires.
What power factor should I use?
Resistive loads such as heaters are 1.0; typical induction motors run 0.8–0.9. Use the cos φ or PF printed on the nameplate when available.