HP to kW Converter
Convert horsepower to kilowatts (hp to kW) for engines, motors and pumps
1 hp = 0.7457 kW. To convert horsepower to kilowatts, multiply the hp by 0.7457, so 200 hp is 149.14 kW.
How to convert horsepower to kilowatts
Mechanical horsepower is 550 foot-pounds-force per second. A foot-pound-force is 0.3048 m × 4.4482216152605 N = 1.3558179 joules, so 550 of them each second is 745.699872 watts, or 0.745699872 kW. Multiplying by that factor converts any hp rating to kW. Going the other way, the kW to hp converter divides by the same number, and the power converter lists every other unit, from watts to BTU per hour.
The common trap is converting the wrong horsepower. If a European brochure lists 150 PS, that is metric horsepower (735.49875 W each), and it is 110.32 kW, not 111.85 kW. US electric motors sometimes use electrical horsepower (exactly 746 W), which differs by a negligible 0.04%. The Horsepower switch above handles both: pick Metric hp (PS) or Electrical hp and the result updates.
Step by step
- Take the rating in mechanical horsepower (hp or bhp).
- Multiply by 0.7457 (more exactly 0.745699872).
- If the rating is metric PS, multiply by 0.73549875 instead.
- Round to one or two decimals of kW.
See it on a scale
Worked examples
A small pump or lawn tractor engine, a large outboard motor and a V8 engine.
5 hp × 0.7456998716 = 3.7284994 kW
= 3.7284994 kW
150 hp × 0.7456998716 = 111.85498 kW
= 111.85498 kW
300 hp × 0.7456998716 = 223.70996 kW
= 223.70996 kW
Is 1 hp equal to 0.75 kW?
Not exactly: 1 mechanical hp is 0.7457 kW, so 0.75 kW is 1.0058 hp. The round 0.75 kW is the IEC motor size conventionally paired with a 1 hp NEMA motor, which is where the shortcut comes from.
The gap is 0.58%, well inside normal motor tolerances, so catalogs treat the two as matching sizes. It shows up more on bigger machines: a 100 hp motor is 74.57 kW, while its usual IEC partner is rated 75 kW, which is 100.58 hp.
- Replacing a motor: match full-load current, speed, frame and mounting as well as power, because NEMA MG 1 and IEC 60072 frames differ.
- Precise work: use 0.745699872 kW per hp, or 0.746 kW if the rating is electrical horsepower.
To estimate what the motor draws, divide its output kW by the efficiency and use the watts to amps calculator. For the circuit itself, follow your local electrical code and have a licensed electrician do the wiring.
How do you calculate kW from torque and rpm?
kW = torque in N·m × rpm ÷ 9,549, because power is torque times angular speed, and 9,549 (60,000 ÷ 2π) turns revolutions per minute into radians per second and watts into kilowatts.
Example: an engine making 400 N·m at 3,000 rpm produces 400 × 3,000 ÷ 9,549 = 125.66 kW, which is 168.52 hp.
In US units the constant is 5,252: hp = torque in lb-ft × rpm ÷ 5,252. That is why the torque and horsepower curves on a US dyno chart cross at 5,252 rpm. A 300 lb-ft engine at that speed makes 300 hp, or 223.71 kW.
If your torque is in lb-ft, the ft-lbs to Nm converter gets you to N·m (300 lb-ft is 406.75 N·m), and the rpm to Hz converter shows shaft speed in revolutions per second. Peak torque and peak power arrive at different engine speeds, so use the torque at the rpm you care about.
HP to kW conversion chart
Values from fractional-horsepower motors to high-performance engines, rounded to three decimals of a kilowatt. Multiply any other hp value by 0.7457.
| Horsepower (hp) | Kilowatts (kW) |
|---|---|
| 0.25 hp | 0.186 kW |
| 0.5 hp | 0.373 kW |
| 0.75 hp | 0.559 kW |
| 1 hp | 0.746 kW |
| 1.5 hp | 1.119 kW |
| 2 hp | 1.491 kW |
| 3 hp | 2.237 kW |
| 5 hp | 3.728 kW |
| 7.5 hp | 5.593 kW |
| 10 hp | 7.457 kW |
| 15 hp | 11.185 kW |
| 20 hp | 14.914 kW |
| 25 hp | 18.642 kW |
| 30 hp | 22.371 kW |
| 40 hp | 29.828 kW |
| 50 hp | 37.285 kW |
| 60 hp | 44.742 kW |
| 75 hp | 55.927 kW |
| 90 hp | 67.113 kW |
| 100 hp | 74.57 kW |
| 115 hp | 85.755 kW |
| 125 hp | 93.212 kW |
| 150 hp | 111.855 kW |
| 175 hp | 130.497 kW |
| 200 hp | 149.14 kW |
| 225 hp | 167.782 kW |
| 250 hp | 186.425 kW |
| 300 hp | 223.71 kW |
| 350 hp | 260.995 kW |
| 400 hp | 298.28 kW |
| 450 hp | 335.565 kW |
| 500 hp | 372.85 kW |
| 600 hp | 447.42 kW |
| 700 hp | 521.99 kW |
| 800 hp | 596.56 kW |
| 1,000 hp | 745.7 kW |
Horsepower vs kilowatts: what is the difference?
Both units rate the same thing, how fast an engine or motor can do work, but they come from different measurement systems and different industries.
| Attribute | Horsepower | Kilowatts |
|---|---|---|
| Symbol | hp | kW |
| System | Imperial (mechanical) | SI |
| Defined as | 745.699872 W | 1,000 W |
| One unit equals | 0.74569987 kW | 1.3410221 hp |
| Standardized by | NIST SP 811, as a non-SI unit (550 ft·lbf/s) | BIPM SI Brochure: the watt with the prefix kilo |
| Versions in use | Several: mechanical (745.7 W), metric PS (735.5 W), electrical (746 W) and boiler (about 9,809.5 W) | One: always exactly 1,000 W |
| Engine test standards | SAE J1349 for US net hp; DIN 70020 behind older German PS figures | ISO 1585 and UN Regulation No. 85 for net power in kW |
| Motor sizes | NEMA MG 1 steps: 1, 1½, 2, 3, 5, 7½, 10 hp and up | IEC steps: 0.75, 1.1, 1.5, 2.2, 5.5, 7.5, 11 kW and up |
| Where you see it | US and UK car specs, outboard and lawn engines, US motor nameplates | EU registration documents, EV spec sheets, IEC motors and most engineering |
4 key differences
- One mechanical horsepower is 0.7457 kW, so the kW figure for any engine is about 25.4% smaller than its hp figure.
- A metric PS is 0.98632 mechanical hp and an electrical hp is 1.0004 mechanical hp, while a kilowatt never varies.
- Converting an SAE J1349 net rating gives net kW; a unit conversion never turns crank power into wheel power or gross into net.
- Motor nameplates in hp and kW follow different size ladders, so a converted rating rarely lands on a standard size in the other system.
US motor nameplates: hp to kW and IEC sizes
US (NEMA) motors are rated in horsepower, while IEC motors used in most other countries come in standard kW sizes. The last column is the IEC rating conventionally paired with each hp size; it is the nearest standard rating from IEC 60072-1, which can be slightly above or below the exact figure, so check the full-load data before substituting one for another. Swapping a motor can change the circuit it needs, so follow your local electrical code and have a licensed electrician check the wiring.
| NEMA rating | Exact kW (745.7 W/hp) | Electrical hp (746 W) | Usual IEC size |
|---|---|---|---|
| ¼ hp | 0.1864 kW | 0.1865 kW | 0.18 kW |
| ⅓ hp | 0.2486 kW | 0.2487 kW | 0.25 kW |
| ½ hp | 0.3728 kW | 0.3730 kW | 0.37 kW |
| ¾ hp | 0.5593 kW | 0.5595 kW | 0.55 kW |
| 1 hp | 0.7457 kW | 0.7460 kW | 0.75 kW |
| 1½ hp | 1.1185 kW | 1.1190 kW | 1.1 kW |
| 2 hp | 1.4914 kW | 1.4920 kW | 1.5 kW |
| 3 hp | 2.2371 kW | 2.2380 kW | 2.2 kW |
| 5 hp | 3.7285 kW | 3.7300 kW | 4 kW |
| 7½ hp | 5.5927 kW | 5.5950 kW | 5.5 kW |
| 10 hp | 7.4570 kW | 7.4600 kW | 7.5 kW |
| 15 hp | 11.1855 kW | 11.1900 kW | 11 kW |
| 20 hp | 14.9140 kW | 14.9200 kW | 15 kW |
| 25 hp | 18.6425 kW | 18.6500 kW | 18.5 kW |
| 30 hp | 22.3710 kW | 22.3800 kW | 22 kW |
| 40 hp | 29.8280 kW | 29.8400 kW | 30 kW |
| 50 hp | 37.2850 kW | 37.3000 kW | 37 kW |
| 75 hp | 55.9275 kW | 55.9500 kW | 55 kW |
| 100 hp | 74.5700 kW | 74.6000 kW | 75 kW |
Is motor horsepower input or output power?
It is output: a motor nameplate's hp or kW rating is the mechanical output at the shaft. The electrical power it draws is higher because no motor is 100% efficient. A 10 hp motor delivers 7.457 kW at the shaft; at 91% efficiency it draws about 8.19 kW from the supply.
That difference matters when you estimate running costs or current. Divide the output kW by the efficiency (and, for AC motors, account for power factor) before using the amps to watts calculator or a watts-to-amps calculation. Nameplates list full-load current directly; in the US, overload protection is set from that nameplate figure, while conductors are sized from the full-load current tables in NEC Article 430. For any wiring or circuit sizing, follow your local electrical code and use a licensed electrician.
Engine ratings: hp to kW, PS and watts
Common horsepower figures converted to kilowatts, metric PS and watts. Use the PS column to compare a US spec with a European brochure.
| Horsepower | Kilowatts | Metric PS | Watts |
|---|---|---|---|
| 1 hp | 0.75 kW | 1 PS | 746 W |
| 5 hp | 3.73 kW | 5.1 PS | 3,728 W |
| 10 hp | 7.46 kW | 10.1 PS | 7,457 W |
| 25 hp | 18.64 kW | 25.3 PS | 18,642 W |
| 50 hp | 37.28 kW | 50.7 PS | 37,285 W |
| 100 hp | 74.57 kW | 101.4 PS | 74,570 W |
| 150 hp | 111.85 kW | 152.1 PS | 111,855 W |
| 200 hp | 149.14 kW | 202.8 PS | 149,140 W |
| 250 hp | 186.42 kW | 253.5 PS | 186,425 W |
| 300 hp | 223.71 kW | 304.2 PS | 223,710 W |
| 400 hp | 298.28 kW | 405.5 PS | 298,280 W |
| 500 hp | 372.85 kW | 506.9 PS | 372,850 W |
| 700 hp | 521.99 kW | 709.7 PS | 521,990 W |
| 1,000 hp | 745.7 kW | 1,013.9 PS | 745,700 W |
What does an engine's horsepower rating measure?
It measures the power available at a stated point, usually the crankshaft, under a stated test procedure, so one engine can carry more than one honest figure.
- Car and truck engines in the US are rated in SAE net horsepower (SAE J1349), measured at the crankshaft with accessories fitted. Wheel horsepower on a chassis dyno is lower.
- Outboard motors are usually rated at the propeller shaft, so a 150 hp outboard's figure already accounts for its gearcase.
- Small engines on mowers and pressure washers are often rated by gross torque rather than hp today, because hp figures were hard to compare between brands.
- Human power: a fit amateur cyclist can hold roughly 200 W for an hour, about 0.27 hp; a trained sprinter can briefly exceed 1 hp.
Quick mental math and mistakes to avoid
Multiply by 3, divide by 4. 200 hp × 0.75 = 150 kW, against the exact 149.14 kW, an error of only 0.6% high. For round numbers, remember that 100 hp is about 74.6 kW and 1,000 hp is about 746 kW.
- Mixing hp and PS. A 200 PS engine is 147.1 kW, while a 200 hp engine is 149.1 kW.
- Mixing kW and kWh. A 5 hp motor is 3.73 kW; running it for two hours uses about 7.46 kWh of shaft energy, plus losses.
- Boiler horsepower is a steam-output unit of about 9.8 kW and has nothing to do with engine hp.
For watts and kilowatts, the watts to kW converter handles the metric prefix step.
Sources and further reading
The standards and references behind the numbers on this page. Links open in a new tab.
Standards and official sources
Further reading
- Mechanical horsepowerWikipedia
HP to kW FAQs
Short, exact answers to what people ask most.
How many kW is 1 hp?
One mechanical horsepower is 0.7457 kW, about three-quarters of a kilowatt.
What is 100 hp in kW?
100 hp equals 74.57 kW.
What is 200 hp in kW?
200 hp is 149.14 kW. If the 200 is metric PS, it is 147.1 kW instead.
What is 300 hp in kW?
300 hp equals 223.71 kW, about 224 kW.
How many kW is a 5 hp motor?
A 5 hp motor delivers 3.73 kW at the shaft. Its IEC equivalent is usually listed as 3.7 kW, and it draws more than that from the supply because of efficiency losses.
Is bhp the same as hp?
Brake horsepower is mechanical horsepower measured at the crankshaft, so it converts with the same factor: 1 bhp = 0.7457 kW. It is higher than wheel horsepower.
What is 50 hp in kW?
50 hp equals 37.28 kW.
How many kW is 400 hp?
400 hp is 298.28 kW, about 298 kW.
What is 125 hp in kW?
125 hp is 93.21 kW. If the rating is 125 PS, it is 91.94 kW instead.
How many kW is 1,000 hp?
1,000 hp equals 745.7 kW, just under three-quarters of a megawatt.
Related conversions
Factors from NIST SP 811 (2008) for mechanical, metric and electrical horsepower and the BIPM SI Brochure (9th ed.) for the watt; engine ratings follow SAE J1349, ISO 1585, UN Regulation No. 85 and DIN 70020, and motor sizes and circuits follow NEMA MG 1, IEC 60072 and NEC (NFPA 70) Article 430. Last updated . How we verify our numbers.