Horsepower to Kilowatts: Three Horsepowers Explained
A 'horsepower' is 735.5 watts in Germany and 745.7 watts in America. That 1.4% gap explains a lot of forum arguments.
6 April 2026 · 5 min read · Automotive
James Watt invented the horsepower as a marketing device — a way to sell steam engines to people who owned horses. It has never fully standardised since.
The variants
| Type | Symbol | Watts | Used in |
|---|---|---|---|
| Mechanical (imperial) | hp | 745.6999 | UK, US |
| Metric | PS, CV, ch | 735.49875 | Europe, Japan |
| Electrical | hp(E) | 746 | US motor ratings |
| Boiler | bhp | 9,809.5 | Steam plant |
Metric horsepower — PS in German, CV in French and Italian, ch in older French — is defined as the power to lift 75 kg by one metre in one second.
The conversions
kW = hp × 0.7457 (mechanical) kW = PS × 0.73550 (metric) hp = kW × 1.34102
A car advertised as 300 PS is 296 hp and 221 kW. The same car sold in the US would be listed at 296 hp — the car is identical, only the label changed. Convert with the horsepower to kilowatts tool.
Where the power is measured
Numbers also differ by measurement point:
- Brake horsepower (bhp) — measured at the crankshaft, on a bench.
- Wheel horsepower (whp) — measured at the wheels on a chassis dyno. Drivetrain losses take 10–15% for front-wheel drive, 15–20% for all-wheel drive.
A car claiming 300 bhp will read around 255 whp on a rolling road. Neither figure is wrong; they measure different things.
Torque is not power
Power is the rate of doing work; torque is rotational force. They are linked by engine speed:
Power (kW) = Torque (N·m) × RPM ÷ 9,549
This is why a diesel with huge torque at 2,000 rpm can produce less peak power than a petrol engine revving to 7,000. See our torque converter for N·m and lb·ft.
Related conversions
This article is for general information. Please verify figures against the relevant standard before using them in critical work. About accuracy