BHP, PS and kW can describe the same power without being the same number
In short
- One mechanical horsepower, commonly written hp or bhp in UK car figures, is about 0.7457 kW.
- One metric horsepower, written PS, is about 0.7355 kW or 0.9863 bhp.
- A different number after conversion does not mean the engine gained or lost power.
- The shop records poster power in bhp and converts a verified PS source rather than relabelling it.
I inherited this problem from finished posters. UK sources often print a PS number and call it bhp, which looks harmless until the same car appears with both values. I now keep the source unit attached, convert it openly, and round only the number that reaches the poster.
What is the difference between BHP, PS and kW?
BHP and PS are different horsepower units, while kW is the SI unit of power. One PS is about 0.7355 kW and one mechanical horsepower is about 0.7457 kW. That makes one PS about 0.9863 bhp.
A unit conversion is not a performance modification. The engine has not changed when a European brochure says 200 PS and a UK poster says 197 bhp. The second number is the first one expressed in another unit.
How do you convert between PS, BHP and kW?
Convert through kilowatts. Multiply PS by 0.735498 or mechanical horsepower by 0.7457 to get kW, then divide by the factor for the unit you want.
| Starting unit | Convert to kW | Useful relationship |
|---|---|---|
| 1 PS | 0.735498 kW | About 0.9863 bhp |
| 1 bhp | 0.7457 kW | About 1.0139 PS |
| 1 kW | 1 kW | About 1.341 bhp or 1.360 PS |
Keep the full factor in the calculation. If one source rounds the PS figure first and another rounds after conversion, their final whole numbers can differ by one without describing different power.
What does brake horsepower mean?
Brake horsepower describes engine power measured with a brake or dynamometer. In UK car specifications, bhp normally uses the mechanical horsepower unit, but the measurement location and correction standard still need checking.
The word “brake” does not turn horsepower into a universal test. A manufacturer can quote engine output under one standard while a rolling road estimates wheel output under another set of conditions. Converting both to kW will not remove that methodological difference.
How should you compare two published power figures?
Check the unit first, then the exact car and measurement basis. Compare market, model year, engine code and test standard before deciding that two converted figures genuinely disagree.
This is the same discipline used for acceleration figures. A label can change the target without changing the car, while a different gearbox or market specification can change the car itself. The guide to why 0 to 60 times vary applies the same source check to performance testing.
Which power unit does the shop print?
The shop prints power in bhp. When a reliable source gives PS, I convert the number to bhp instead of moving the original digits under a different label.
That rule is why a 200 PS source becomes 197 bhp in the catalogue. It also means the original source and conversion need to remain in the model record, where somebody can check the decision later. The specification-checking article explains the rest of that sign-off process.
Which standards support these conversions?
The BIPM defines the watt as the SI unit of power. European legislation records 1 metric horsepower as 0.735498 kW and 1 mechanical horsepower as 0.7457 kW.
See the current BIPM SI Brochure and the European conversion record. The legislation uses the older labels CV and hp, but the conversion factors are the point used here. A conversion alone does not establish which figure belongs to a particular car.
Published cars carry that decision in their signed records. Browse the catalogue specification blocks rather than applying a generic internet number to the drawing.
Questions people actually ask
- Is PS the same as BHP?
- No. PS is metric horsepower and bhp is normally mechanical horsepower measured at the engine in UK car usage. One PS is about 0.9863 bhp, so the numbers are close but should not be copied under the other label.
- How much is 200 PS in BHP?
- Two hundred PS is about 197 bhp after conversion. It is also about 147 kW. Published figures may round at different stages, so a one-unit difference can be rounding rather than a different engine output.
- How do you convert BHP to kW?
- Multiply mechanical horsepower by approximately 0.7457 to get kilowatts. For example, 200 bhp is about 149 kW. Keep more decimal places during the calculation and round only the displayed result.
- Why do two sources give different power figures for the same car?
- First check whether one uses PS and the other bhp or kW. If conversion does not reconcile them, compare the market, model year, engine version, measurement standard and whether the figure is a manufacturer claim or an individual test.
Written by Jonathan in Derby. Last updated .