What is Brake Power (BP)?

Brake Power (BP) represents the actual power available at the output shaft of an engine (usually the crankshaft). Unlike Indicated Power, which is the theoretical power generated inside the combustion chamber, Brake Power accounts for the energy lost due to internal friction, pumping, and mechanical inefficiencies within the engine components. It is the real-world performance metric used by automotive engineers to determine how much work an engine can perform.

How to Use the Brake Power Calculator

Using this tool is straightforward for enthusiasts and engineers alike:

1. Select Your Unit: Choose between Metric (Newton-meters and kilowatts) or Imperial (Pound-feet and Horsepower) systems.
2. Enter Torque: Input the torque measured from the dynamometer at a specific RPM.
3. Enter RPM: Input the revolutions per minute (RPM) at which the torque was recorded.
4. Calculate: Click the button to see the results instantly.

The Formula Behind Brake Power

The calculation depends on the units being used. For the Metric system, the formula is:

BP (kW) = (2 * π * Torque * RPM) / 60,000

For the Imperial system, commonly used in the United States, the formula is:

BP (HP) = (Torque * RPM) / 5252

Frequently Asked Questions

Why is it called "Brake" Power?

The term originates from the historical method of measuring engine output using a "Prony Brake" or similar braking device. This device applied a frictional load (a brake) to the engine to measure the torque it could produce against resistance.

What is the difference between BHP and HP?

While often used interchangeably, Brake Horsepower (BHP) specifically refers to the power measured at the flywheel without losses from the gearbox and drivetrain. General Horsepower (HP) might refer to the power measured at the wheels (Wheel Horsepower), which is always lower due to transmission losses.