BHP, HP, PS and kW explained
Vehicle power is commonly quoted in bhp, hp, PS or kW. The units are close enough to be confused, but not identical enough to swap the numbers without converting them.
The useful reference relationships
In ordinary UK vehicle discussions, bhp is commonly used for mechanical brake horsepower. Always check the source unit when comparing manufacturer figures from different markets.
Power conversion table
| Mechanical hp / bhp | kW | PS |
|---|---|---|
| 50 bhp | 37.3 kW | 50.7 PS |
| 75 bhp | 55.9 kW | 76.0 PS |
| 100 bhp | 74.6 kW | 101.4 PS |
| 150 bhp | 111.9 kW | 152.1 PS |
| 200 bhp | 149.1 kW | 202.8 PS |
| 300 bhp | 223.7 kW | 304.2 PS |
| 400 bhp | 298.3 kW | 405.5 PS |
kW to BHP and PS to BHP quick answers
| Starting value | BHP / mechanical HP | kW | PS |
|---|---|---|---|
| 100 kW | 134.1 | 100.0 | 136.0 |
| 150 kW | 201.2 | 150.0 | 203.9 |
| 200 PS | 197.3 | 147.1 | 200.0 |
| 300 PS | 295.9 | 220.6 | 300.0 |
To convert kW to BHP, multiply by about 1.341. To convert PS to BHP, multiply by about 0.9863. Use the power-unit converter when you need a different value or more precision.
Power and torque are related through engine speed
Torque describes twisting force; power describes the rate of doing work. At a given RPM, they can be related mathematically. In imperial units a commonly used relationship is:
This is why two engines with similar peak torque can have very different peak power if the torque occurs across different engine-speed ranges.
Why power-to-weight often tells you more than power alone
A 200 bhp car weighing 1,000 kg has 200 bhp/tonne. A 300 bhp car weighing 2,000 kg has 150 bhp/tonne. That does not predict acceleration by itself—traction, gearing, aerodynamics and power delivery matter—but it explains why headline engine power is not a complete performance comparison.
Crank power and wheel power are not interchangeable
Manufacturer power figures are commonly quoted at the engine or crank, while a rolling-road result is measured at the driven wheels. The gap is not a universal fixed percentage: transmission type, tyres, test procedure, temperatures and the dyno itself all influence a wheel-power result. That is why the WHP to HP Calculator exposes the drivetrain assumption rather than claiming an exact conversion.
For comparing two published vehicles, use figures stated on the same basis. Converting PS to kW is an exact unit conversion; converting wheel power to crank power is an estimate.