What is the Difference Between Horsepower and Brake Horsepower?

🆚 Go to Comparative Table 🆚

The main difference between horsepower (HP) and brake horsepower (BHP) lies in how they are measured and what they represent.

  • Horsepower (HP) measures the power generated by the engine, expressed in foot-pounds per second (1 HP = 550 foot-pounds per second). It is a unit of measurement used to describe the rate at which work is done or energy is expended.
  • Brake Horsepower (BHP) refers to the horsepower of the car after taking into consideration friction. In other words, BHP accounts for the power loss due to friction, which is why BHP is always less than a car's horsepower. BHP measures how much of the power produced by the engine is sent to the wheels.

To summarize:

  • HP measures the power generated by the engine.
  • BHP measures the power sent to the wheels after accounting for friction and other losses.

Another related term is Wheel Horsepower (WHP), which measures the actual amount of power that makes it to the ground. This measure is taken after accounting for all losses from the engine, transmission, and driveline.

Comparative Table: Horsepower vs Brake Horsepower

The main difference between horsepower (HP) and brake horsepower (BHP) lies in the measurement method and the factors they consider. Here is a table comparing the two:

Feature Horsepower (HP) Brake Horsepower (BHP)
Definition HP is the output horsepower rating of an engine (1 HP = 746 Watts). BHP is the input brake horsepower of an engine, measured at the engine's flywheel without considering losses caused by the generator, gearbox, water pump, and other auxiliary parts.
Factor Considered HP takes into account frictional losses in power from the engine. BHP takes into account frictional losses in power from the engine.
Measurement HP is measured with all the accessories attached to the engine. BHP is measured with minimal or no accessories attached to the engine.
Usage HP is commonly used in automotive circles, especially in the United States. BHP is the traditional way of measuring a car's power output in the UK and is more commonly used in UK car magazines.

In summary, HP is the output horsepower rating of an engine, while BHP is the input brake horsepower of an engine. BHP measures the pure mechanical output power from the engine without considering losses caused by auxiliary parts, while HP takes into account these losses. HP is more commonly used in the United States, while BHP is more prevalent in the UK.