HP to kW converter (and kW to hp)
Converting horsepower to kilowatts multiplies the horsepower by the kilowatts in one horsepower: 0.745699872 kW for mechanical horsepower, 0.746 kW for electrical horsepower and 0.73549875 kW for metric horsepower. Converting kW to hp divides by the same figure.
Convert hp and kW
Updates as the values change. The page address keeps the values for sharing.
US motor nameplates state horsepower as shaft output. The power drawn from the supply is larger by the motor's efficiency, so the converter can add an efficiency to turn output horsepower into electrical input kilowatts, the figure that relates to current.
Formulas
Mechanical hp (US)
The imperial horsepower of 550 ft·lbf per second, used on US motor nameplates, engines and pumps. One hp is 745.7 W.
Electrical hp
Defined as exactly 746 W and used in some electrical references; it differs from mechanical horsepower by less than 0.05%.
Metric hp (PS)
Defined from 75 kgf·m per second and used on equipment from Europe and Asia, sometimes marked PS or CV. It is about 1.4% smaller than mechanical horsepower.
Motor input
Efficiency η is the nameplate or data-sheet value as a fraction. A 90%-efficient motor delivering 7.457 kW at the shaft draws 8.286 kW from the supply.
Without an efficiency the converter treats horsepower and kilowatts as the same power in two units. With one, it reports both shaft output and electrical input.
Worked examples
A 10 hp motor, 91% efficient
A US nameplate in mechanical horsepower, with the efficiency listed on the motor.
Mechanical hp (US, 745.7 W): 1 hp = 0.745699872 kWkW = 10 hp × 0.745699872 = 7.457 kWInput = output ÷ η = 7.457 kW ÷ 0.91 = 8.195 kW
The shaft delivers 7.457 kW and the motor draws 8.195 kW from the supply. For conductor and protection sizing the NEC uses table currents rather than either figure.
A 75 kW pump motor expressed in horsepower
A motor specified in kilowatts converted to US mechanical horsepower.
Mechanical hp (US, 745.7 W): 1 hp = 0.745699872 kWhp = 75 kW ÷ 0.745699872 = 100.577 hp
75 kW is 100.58 hp. A 100 hp NEMA motor delivers 74.57 kW, so the two ratings describe nearly the same machine; the data sheets settle which one a specification calls for.
A 5 PS compressor motor from a metric data sheet
Metric horsepower, converted to kW and then compared with mechanical horsepower.
Metric hp (735.5 W): 1 hp = 0.73549875 kWkW = 5 hp × 0.73549875 = 3.677 kW
5 PS is 3.677 kW, or 4.932 mechanical hp.
Conversion tables
| hp (hp) | Mechanical hp (kW) | Electrical hp (kW) | Metric hp (kW) |
|---|---|---|---|
| 0.25 | 0.186 | 0.187 | 0.184 |
| 0.33 | 0.246 | 0.246 | 0.243 |
| 0.5 | 0.373 | 0.373 | 0.368 |
| 0.75 | 0.559 | 0.560 | 0.552 |
| 1 | 0.746 | 0.746 | 0.735 |
| 1.5 | 1.119 | 1.119 | 1.103 |
| 2 | 1.491 | 1.492 | 1.471 |
| 3 | 2.237 | 2.238 | 2.206 |
| 5 | 3.728 | 3.730 | 3.677 |
| 7.5 | 5.593 | 5.595 | 5.516 |
| 10 | 7.457 | 7.460 | 7.355 |
| 15 | 11.185 | 11.190 | 11.032 |
| 20 | 14.914 | 14.920 | 14.710 |
| 25 | 18.642 | 18.650 | 18.387 |
| 30 | 22.371 | 22.380 | 22.065 |
| 40 | 29.828 | 29.840 | 29.420 |
| 50 | 37.285 | 37.300 | 36.775 |
| 75 | 55.927 | 55.950 | 55.162 |
| 100 | 74.570 | 74.600 | 73.550 |
| kW (kW) | Mechanical hp (hp) | Metric hp (hp) |
|---|---|---|
| 0.25 | 0.34 | 0.34 |
| 0.5 | 0.67 | 0.68 |
| 0.75 | 1.01 | 1.02 |
| 1 | 1.34 | 1.36 |
| 1.5 | 2.01 | 2.04 |
| 2.2 | 2.95 | 2.99 |
| 3 | 4.02 | 4.08 |
| 4 | 5.36 | 5.44 |
| 5.5 | 7.38 | 7.48 |
| 7.5 | 10.06 | 10.20 |
| 11 | 14.75 | 14.96 |
| 15 | 20.12 | 20.39 |
| 18.5 | 24.81 | 25.15 |
| 22 | 29.50 | 29.91 |
| 30 | 40.23 | 40.79 |
| 37 | 49.62 | 50.31 |
| 45 | 60.35 | 61.18 |
| 55 | 73.76 | 74.78 |
| 75 | 100.58 | 101.97 |
| 90 | 120.69 | 122.37 |
| 110 | 147.51 | 149.56 |
Generated by the converter's engine with no efficiency applied. The kW values in the second table are the IEC motor ratings common on equipment built for 50 Hz markets.
Common mistakes
Treating nameplate horsepower as the power drawn
Horsepower on a motor nameplate is shaft output. The supply delivers more, by the factor 1 ÷ efficiency, so a 10 hp motor at 90% efficiency draws about 8.3 kW, not 7.5 kW.
Converting metric horsepower as mechanical
A machine rated 100 PS develops 73.5 kW, not 74.6 kW. On equipment documented outside the US, the unit is worth confirming before comparing ratings.
Sizing motor conductors from converted kW
NEC 430.6(A)(1) requires the full-load currents of Tables 430.247 to 430.250, not currents calculated from kW or nameplate amps, for conductor and short-circuit protection sizing. The motor FLA calculator follows that approach.
Rounding 1 hp to 0.75 kW
0.75 kW is an IEC motor size, not an exact conversion. One mechanical horsepower is 0.7457 kW; the 0.6% difference grows to several kilowatts across a large motor list.
Frequently asked questions
How many kW is 1 hp?
One mechanical horsepower is 0.745699872 kW, often rounded to 0.746 kW. One electrical horsepower is exactly 0.746 kW and one metric horsepower 0.73549875 kW.
How many hp is 1 kW?
1 kW is 1.3410 mechanical hp or 1.3596 metric hp.
Does a 10 hp motor use 7.5 kW?
It delivers 7.46 kW at the shaft at full load. Its input is higher; at 90% efficiency it draws 8.29 kW from the supply.
Which horsepower is used in the US?
Mechanical (imperial) horsepower, 550 ft·lbf per second, is the unit on NEMA motor nameplates. Electrical horsepower appears in some references; metric horsepower comes with imported equipment.
How is motor horsepower converted to amps?
Through voltage, phase, power factor and efficiency, which the HP to amps calculator applies. For NEC conductor and protection sizing, the motor full-load current tables are used instead of a calculated value.