To convert hp to kW, multiply by 0.7457: one mechanical horsepower is 550 ft·lbf/s, about 745.6999 W. Formula: kW = mechanical hp × 0.745699871582; kW = PS × 0.73549875. For example, 10 hp ≈ 7.457 kW and 100 hp ≈ 74.57 kW. Metric horsepower (PS) is 735.49875 W and electric horsepower is exactly 746 W.
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How to use the hp to kW converter
- Enter the power in horsepower, for example 25.
- Read the hp to kw converter result: 25 × 0.7457 ≈ 18.64 kW.
- Check which horsepower the source uses; for PS, multiply by 0.7355 instead.
What is the HP to kW formula?
kilowatts = mechanical horsepower × 0.7457
The reverse is mechanical horsepower = kilowatts × 1.3410221 (approximately).
One mechanical horsepower is defined as 550 foot-pounds-force per second, which works out to about 745.699872 W. The multiplier 0.7457 is rounded to six significant digits; the hp to kw calculator uses the full-precision value.
What are mechanical horsepower and kilowatts?
Power is the rate of doing work or using energy. The SI unit is the watt (W), one joule per second. One mechanical horsepower is about 745.7 W, one metric horsepower about 735.5 W, and air conditioners are rated in BTU per hour or tons of refrigeration.
- Mechanical horsepower (hp): 1 hp = 745.6998716 W (US/Imperial unit).
- Kilowatt (kW): 1 kW = 1,000 W (SI unit).
Hp to kw worked examples
- A 150 hp car engine: 150 × 0.7457 = 111.855 kW
- A 5 hp pump: 5 × 0.7457 = 3.7285 kW
- A 300 hp engine: 300 × 0.7457 = 223.71 kW
Conversion chart
| hp | kW | hp | kW |
|---|---|---|---|
| 1 | 0.7457 | 200 | 149.14 |
| 5 | 3.7285 | 250 | 186.42 |
| 10 | 7.457 | 300 | 223.71 |
| 25 | 18.6425 | 400 | 298.28 |
| 50 | 37.285 | 500 | 372.85 |
| 75 | 55.9275 | 600 | 447.42 |
| 100 | 74.57 | 700 | 521.99 |
| 150 | 111.85 | 1,000 | 745.7 |
Values are rounded to four decimal places, or two for results of 100 or more.
Quick mental conversion
Multiply by 0.75 for a quick estimate (exact 0.7457).
Which horsepower?
| Horsepower | Watts |
|---|---|
| Mechanical (imperial) hp, used here | 745.70 |
| Metric hp (PS, CV) | 735.50 |
| Electrical hp | 746 |
European car specifications often list PS (metric horsepower); 100 PS = 73.55 kW.
Mechanical horsepower from kilowatts: reverse chart
Going the other way, mechanical horsepower = kilowatts × 1.3410221. Common values:
| kilowatts | mechanical horsepower |
|---|---|
| 1 | 1.341022 |
| 2 | 2.682044 |
| 5 | 6.70511 |
| 10 | 13.41022 |
| 20 | 26.82044 |
| 50 | 67.05111 |
| 100 | 134.1022 |
| 500 | 670.511 |
| 1,000 | 1,341.022 |
Electric motor sizes in kW
US motor nameplates use hp; IEC motors use kW. Common sizes:
| hp | kW (mechanical hp) | Nearest IEC rating |
|---|---|---|
| 1 | 0.746 | 0.75 kW |
| 2 | 1.491 | 1.5 kW |
| 5 | 3.728 | 3.7 kW |
| 10 | 7.457 | 7.5 kW |
| 20 | 14.914 | 15 kW |
| 50 | 37.285 | 37 kW |
| 100 | 74.57 | 75 kW |
The kW figure is shaft output. The power drawn from the supply is higher, by the motor efficiency.
Three phase motor current
For a 3 phase motor, input current is I = P ÷ (√3 × V × efficiency × power factor). A 10 hp (7.457 kW) motor on 460 V with 90% efficiency and 0.85 power factor draws about 7,457 ÷ (1.732 × 460 × 0.9 × 0.85) ≈ 12.2 A. Nameplate and code tables should be used for wire and breaker sizing. Use the kW to hp converter for the reverse and the power unit converter for BTU/h and other units.
Car ratings in Europe
European car brochures list power in kW, often with metric horsepower (PS) beside it. A 110 kW engine is about 147.5 mechanical hp, or about 149.6 PS. The two horsepower units differ by about 1.4%, so check which one a spec uses before comparing cars.
For electric motors, the nameplate horsepower is the output at the shaft. A 10 hp motor delivers about 7.46 kW. If it runs at 90% efficiency, it draws about 8.29 kW from the supply. Size wiring and energy costs from the input, not the output. An hp to kw conversion gives the output side.
Generators and air compressors in some markets list both units on the label, and their ratings may refer to peak rather than continuous output. A 5 kW peak generator might run continuously at 4.5 kW, about 6 hp. When choosing a motor to drive a pump, match the pump’s shaft power in kW and then pick the next standard horsepower size up.
Older tractors may be rated in PTO horsepower, measured at the power take-off shaft, which reads lower than engine horsepower.
Related converters and calculators
Related conversions:
- kW to hp: kW to hp
- Power unit converter: W and BTU/h
- Electricity calculator: energy cost
- Ohm’s law calculator: V, I, R
- Torque unit converter: N·m and ft·lb
Sources
NIST Special Publication 811, Appendix B; US DOE: Determining electric motor load and efficiency.
Questions about this calculator
How many kW is 1 hp?
About 0.7457 kW (mechanical horsepower).
How do I convert hp to kW?
Multiply by 0.7457. For example, 150 hp ≈ 111.9 kW.
What is PS in kW?
1 PS (metric horsepower) = 0.73549875 kW.
Is bhp the same as hp?
Brake horsepower is measured at the shaft; it uses the same 745.7 W unit.
What current does a 10 hp 3 phase motor draw?
About 12 A at 460 V, depending on efficiency and power factor.
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
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