Converting kW to HP: horsepower and kilowatt calculations
How many HP is a kW? Converting between horsepower and kilowatts
1 kW is approximately 1.341 HP, and 1 HP is approximately 0.746 kW. Here, HP means mechanical horsepower. With metric horsepower, expressed as PS, 1 kW is approximately 1.360 PS. Different horsepower definitions are a common reason for finding different conversion results online.
Kilowatts (kW) and horsepower (HP) express the same physical quantity: power. Describing an electric motor's shaft output in HP instead of kW does not change the power it produces.
kW ↔ HP / PS converter
Choose the conversion direction and horsepower definition. The result updates when you change a value. A decimal point or comma is accepted; do not use thousands separators.
Try an example:
7.5 kW ÷ 0.745699872 ≈ 10.0577 HP
1 HP ≈ 0.745699872 kW
This tool converts power units. It does not calculate motor efficiency, current or starting requirements.
Why are HP and PS different?
HP = kW × 1.34102209
kW = HP × 0.745699872
This definition is used in the HP table column and the calculator's default setting.
PS = kW × 1.35962162
kW = PS × 0.73549875
Metric horsepower is commonly encountered in automotive specifications.
Electric horsepower has a separate definition of 1 HP = 746 W, also available in the calculator. A motor being electrically powered does not, by itself, establish which horsepower definition its documentation uses. Check the manufacturer's stated unit convention.
Common kW values converted to HP and PS
These are mathematical conversions, rounded to three decimal places. They are not a list of manufacturers' nominal ratings or guaranteed interchangeable motors.
| kW | HP (mechanical) | PS |
|---|---|---|
| 0.37 | 0.496 | 0.503 |
| 0.55 | 0.738 | 0.748 |
| 0.75 | 1.006 | 1.020 |
| 1.1 | 1.475 | 1.496 |
| 1.5 | 2.012 | 2.039 |
| 2.2 | 2.950 | 2.991 |
| 3 | 4.023 | 4.079 |
| 4 | 5.364 | 5.438 |
| 5.5 | 7.376 | 7.478 |
| 7.5 | 10.058 | 10.197 |
| 11 | 14.751 | 14.956 |
| 15 | 20.115 | 20.394 |
| 22 | 29.502 | 29.912 |
| 30 | 40.231 | 40.789 |
| 37 | 49.618 | 50.306 |
| 55 | 73.756 | 74.779 |
| 75 | 100.577 | 101.972 |
| 110 | 147.512 | 149.558 |
| 160 | 214.564 | 217.539 |
Why is a 7.5 kW motor often called “10 HP”? Industrial power classes are frequently matched using rounded nominal values. The numerical conversions are 7.5 kW ≈ 10.058 HP and 10 HP ≈ 7.457 kW. Similarly, 2.2 kW converts to about 2.950 HP but may be described as a “3 HP class” rating. Use the actual nameplate and manufacturer's data for selection.
Does a 7.5 kW motor draw 7.5 kW from the supply?
A motor's kW or HP rating usually describes its mechanical shaft output under rated conditions. Electrical input is higher because of motor losses. For a motor delivering 7.5 kW at the shaft with 90% efficiency at that operating point:
The difference of approximately 0.83 kW represents motor losses. If a drive supplies the motor, drive losses must be considered separately.
Do not divide by efficiency when converting kW to HP. Unit conversion expresses the same power in another unit; an input–output calculation is a different operation. Calculating motor current also requires voltage, the phase arrangement, efficiency and power factor.
The rated output does not mean the motor always consumes the same electrical power. Consumption changes with load; kWh on an electricity bill also depends on operating time. kVA is not directly interchangeable with kW or HP either.
Why can two motors with the same HP rating perform differently?
Power alone does not specify torque; rotational speed is also needed. For shaft power P in kW, speed n in rpm and torque T in N·m, the approximate relationship is T = 9550 × P ÷ n.
Calculated shaft torque at the stated power and speed.
At the same power, twice the speed means approximately half the torque.
These represent two separate operating points; they do not mean a motor automatically maintains constant power when slowed down. In the constant-torque region, mechanical power decreases as speed decreases. Gearbox selection must consider ratio, output speed, torque capacity and losses together.
Using HP ratings to select a motor and drive
A motor specified as 10 HP converts to approximately 7.457 kW. That result alone does not establish that every 7.5 kW drive will suit it. Variable frequency drive selection also requires comparison of motor rated current, operating voltage, load torque and the drive's overload capability.
The star–delta connection rating matters for supply compatibility, while starting current matters during acceleration. Contactors and thermal overload relays also require more than an HP figure for correct selection.