kW to amps
Enter the power in kW and the supply voltage to find the current in amps, read on a live ammeter with the next standard breaker size.
Inputs
Current on the ammeter
How kW to amps calculator works
The kW to amps calculator converts power in kilowatts (kW) into current in amperes (A) with 4 inputs: power, voltage, power factor and current type. The calculator divides watts by volts × PF for single phase, by √3 × volts × PF for three phase and by volts for direct current (DC), then suggests a breaker at 125% of the current.
I = P × 1000 / (k × V × PF)5 kW at 230 V and PF 0.9 gives 24.15 A and a 32 A breaker. The same 5 kW on a 400 V three-phase supply draws 8.02 A per line. The ammeter dial shows the current against its full scale.
kW to amps formula
The kW to amps formula is I(A) = P(kW) × 1,000 / (V × PF) for single-phase AC. There are 3 kW to amps formulas, one for each current type: DC, single-phase AC and three-phase AC.
Direct current (DC)
I = P × 1000 / V2 kW × 1,000 / 48 V = 41.67 A
Single-phase AC
I = P × 1000 / (V × PF)5 kW × 1,000 / (230 V × 0.9) = 24.15 A
Three-phase AC
I = P × 1000 / (√3 × V × PF)5 kW × 1,000 / (1.732 × 400 V × 0.9) = 8.02 A
The National Electrical Code (NEC, NFPA 70) limits continuous loads to 80% of the breaker rating, so the breaker must be at least 125% of the calculated amps. Power factor (PF) values fall into 4 groups: 1 for heaters, kettles and incandescent lamps, 0.95–0.99 for electronics with power factor correction, 0.8–0.9 for loaded induction motors and 0.5–0.7 for lightly loaded motors.
kW to amps conversion chart
The kW to amps conversion chart lists the amps drawn by 14 loads from 0.5 kW to 100 kW at 6 supply voltages: 120 V, 230 V and 240 V single phase and 208 V, 400 V and 480 V three phase. The chart uses a power factor of 1.
| kW | 120 V1-phase | 230 V1-phase | 240 V1-phase | 208 V3-phase | 400 V3-phase | 480 V3-phase |
|---|---|---|---|---|---|---|
| 0.5 kW | 4.17 | 2.17 | 2.08 | 1.39 | 0.72 | 0.6 |
| 1 kW | 8.33 | 4.35 | 4.17 | 2.78 | 1.44 | 1.2 |
| 1.5 kW | 12.5 | 6.52 | 6.25 | 4.16 | 2.17 | 1.8 |
| 2 kW | 16.67 | 8.7 | 8.33 | 5.55 | 2.89 | 2.41 |
| 3 kW | 25 | 13.04 | 12.5 | 8.33 | 4.33 | 3.61 |
| 5 kW | 41.67 | 21.74 | 20.83 | 13.88 | 7.22 | 6.01 |
| 7.5 kW | 62.5 | 32.61 | 31.25 | 20.82 | 10.83 | 9.02 |
| 10 kW | 83.33 | 43.48 | 41.67 | 27.76 | 14.43 | 12.03 |
| 15 kW | 125 | 65.22 | 62.5 | 41.64 | 21.65 | 18.04 |
| 20 kW | 166.67 | 86.96 | 83.33 | 55.51 | 28.87 | 24.06 |
| 30 kW | 250 | 130.43 | 125 | 83.27 | 43.3 | 36.08 |
| 50 kW | 416.67 | 217.39 | 208.33 | 138.79 | 72.17 | 60.14 |
| 75 kW | 625 | 326.09 | 312.5 | 208.18 | 108.25 | 90.21 |
| 100 kW | 833.33 | 434.78 | 416.67 | 277.57 | 144.34 | 120.28 |
Divide a chart value by the power factor for motors: 10 kW at 400 V draws 14.43 A at PF 1 and 16.98 A at PF 0.85.
kW to amps Excel formula
The kW to amps Excel formula is =A2*1000/(B2*C2) with kW in A2, volts in B2 and power factor in C2. Use =A2*1000/(SQRT(3)*B2*C2) for three phase and =A2*1000/B2 for DC.
| A | B | C | D | E | |
|---|---|---|---|---|---|
| 1 | kW | Volts | PF | Amps | Formula in D |
| 2 | 5 | 230 | 0.9 | 24.15 | =ROUND(A2*1000/(B2*C2),2) |
| 3 | 5 | 400 | 0.9 | 8.02 | =ROUND(A3*1000/(SQRT(3)*B3*C3),2) |
| 4 | 2 | 48 | 1 | 41.67 | =ROUND(A4*1000/B4,2) |
Add =D2*1.25 in column E to get the minimum breaker rating for continuous loads.
kW to amps equation
The kW to amps equation is I = P × 1,000 / (k × V × PF), where k is 1 for single phase and √3 (1.732) for three phase.
- I
- Current in amperes (A)
- P
- Real power in kW
- k
- 1 for DC and single phase, √3 for three phase
- V
- Voltage in volts (V)
- PF
- Power factor, 1 for DC
Current falls as voltage rises: 3 kW draws 25 A at 120 V and 12.5 A at 240 V, half the current at double the voltage.
kW to amps FAQ
How many amps is 1 kW?
1 kW is 4.35 A at 230 V, 4.17 A at 240 V and 8.33 A at 120 V single phase, at a power factor of 1. 1 kW draws 1.44 A per line at 400 V three phase.
How many amps is 5 kW?
5 kW is 21.74 A at 230 V and 20.83 A at 240 V single phase, at a power factor of 1. 5 kW draws 41.67 A at 120 V and 7.22 A per line at 400 V three phase.
What breaker size do I need for 7 kW?
7 kW needs a 40 A breaker at 230 V: 7 kW draws 30.43 A, and 125% of 30.43 A is 38.04 A. At 240 V, 7 kW draws 29.17 A and needs a 40 A breaker.
Does power factor change kW to amps?
Yes, a lower power factor increases the amps for the same kW. 5 kW at 230 V draws 21.74 A at PF 1 and 27.17 A at PF 0.8.