HP to kW Converter
Convert horsepower, brake horsepower, metric PS, kilowatts and BTU/h, with drivetrain loss and power-to-weight.
About this tool
HP to kW Converter
Convert horsepower, brake horsepower, metric PS, kilowatts and BTU/h, with drivetrain loss and power-to-weight.
The HP to kW Converter moves a power figure between mechanical horsepower, metric PS, kilowatts, watts, BTU/h and related units using their exact definitions rather than rounded factors: mechanical horsepower is 550 ft·lbf/s = 745.6998716 W, metric horsepower is 75 kgf·m/s = 735.49875 W, and electrical horsepower is defined as exactly 746 W. It also separates crankshaft power from wheel power using a drivetrain-loss allowance, and reports power-to-weight in hp, kW and PS per tonne. Built for anyone comparing a German PS figure against a US horsepower figure, or a dyno printout against a manufacturer's claim.
How to use HP to kW Converter
- 1
Open HP to kW Converter on AltFTool — it loads instantly in your browser.
- 2
Type the figure into "Power value" and pick its "Unit of that value" — kilowatts, mechanical horsepower, metric PS, watts, electrical horsepower, BTU/h, ft·lbf/s, kgf·m/s or boiler horsepower.
- 3
Choose a "Drivetrain (for crank vs wheel power)", from no loss up to All-wheel drive automatic at about 25%, and optionally add "Vehicle weight (optional)" in kilograms or pounds.
- 4
The headline gives the kilowatt figure — 200 hp reads 149.14 kW — with every other unit listed under it, plus "Crank versus wheel power" and "Power-to-weight" in hp, kW and PS per tonne; "Copy result" copies the lot.
Why use HP to kW Converter
Exact definitions
Uses 745.6998716 W and 735.49875 W rather than the rounded 746 and 735 that drift by a horsepower or more on big engines.
PS and hp kept apart
Metric PS reads about 1.4% higher than mechanical hp for the same engine, which is why the same car is quoted differently in different markets.
Crank versus wheel
Applies a drivetrain loss so a dyno figure and a brochure figure can be compared like for like.
Common use cases
- Comparing a car advertised at 150 kW in Europe with one advertised at 201 hp in the US
- Translating a chassis-dyno wheel-horsepower result back to the crank figure a manufacturer quotes
- Working out power-to-weight in hp per tonne to compare two cars of different mass
Frequently asked questions
How many kW is 200 hp?
149.14 kW. One mechanical horsepower is exactly 745.6998716 watts, so 200 hp × 745.6998716 = 149,140 W. Going the other way, 100 kW is 134.10 hp.
What is the difference between hp, bhp and PS?
PS is a genuinely different unit — metric horsepower, 75 kgf·m/s or 735.49875 W — so 200 hp equals 202.77 PS, about 1.4% higher. Bhp is not a different unit at all: it is mechanical horsepower measured at the crankshaft on a brake dynamometer, as opposed to wheel horsepower measured at the tyres.
How much power is lost in the drivetrain?
Roughly 10-15% for front- and rear-wheel drive and 20-25% for all-wheel drive, with automatics at the higher end of each range. A 300 hp crank figure through a rear-drive manual therefore reads around 255 hp at the wheels. These are rules of thumb, not measured constants — actual loss varies with gearing, tyres, temperature and the dyno itself.
Is 1 hp exactly 746 watts?
Only electrical horsepower is, by definition, and that unit is used on US electric motor nameplates. Mechanical horsepower — the one used for engines — is 550 ft·lbf/s, which works out to 745.6998716 W. The difference is about 0.04%, negligible on a small motor but worth a fraction of a horsepower on a 500 hp engine.
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