What is Brake Horsepower?

Malcolm Tatum
Malcolm Tatum

Brake horsepower (BHP) is the amount of power generated by a motor without taking into consideration any of the various auxiliary components that may slow down the actual speed of the motor. Sometimes referred to as pure horsepower, brake horsepower is measured within the engine's output shaft. Depending on the configuration of the engine, the point on the output shaft that is the focus of the measurement is the engine dynamometer.

When calculating brake horsepower, it is important to consider the entire load of the system's electric motor.
When calculating brake horsepower, it is important to consider the entire load of the system's electric motor.

The reference to this type of horsepower measurement as brake horsepower has its origins in the braking systems that were used on some of the first automobiles in the early 20th century. In many instances, cars were equipped with a hand brake that would slow the forward projection of the vehicle. This same hand brake was also used in the manufacturing process to gauge the amount of torque created within the motor, making sure the output was within acceptable limits.

An air brake.
An air brake.

In the actual calculation of brake horsepower, it is necessary to consider the total load of the electric motor. This means disregarding any drain on the power that is due to the water pump, generator, or the gearbox that work in conjunction with the motor of the vehicle. The amount of power loss that occurs due to the action of various belts and pulleys is also added back into the base figure, making it possible to determine the true amount of pure horsepower being generated by the motor.

Understanding the brake horsepower of a motor is key to ensuring the output is strong enough to drive both the motor and any auxiliary components. By measuring brake horsepower, it is possible to determine how much power must be produced to allow the motor to function at peak efficiency with the core functions. At the same time, calculating a proper brake horsepower that will supply an adequate amount of power to all complimentary devices found under the hood will ensure that many of the one-time extras available on vehicles that are now considered standard features will work properly. As a third benefit, measuring brake horsepower also helps manufacturers to produce engines that meet all current safety regulations for engine types within a given classification.

Malcolm Tatum
Malcolm Tatum

After many years in the teleconferencing industry, Michael decided to embrace his passion for trivia, research, and writing by becoming a full-time freelance writer. Since then, he has contributed articles to a variety of print and online publications, including wiseGEEK, and his work has also appeared in poetry collections, devotional anthologies, and several newspapers. Malcolm’s other interests include collecting vinyl records, minor league baseball, and cycling.

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Discussion Comments


I always wondered what bhp meant: brake horse power. Thanks for the heads up.


In the states any time you see a number from a manufacture claiming "horsepower" it is brake horsepower. You will often talk to people who know cars talking about wheel horsepower measured on a dynamometer The typical loss of drivetrain and accessory load is 15-20 percent, so take the manufactures number and subtract off that loss to get an approximate wheel horsepower number.


brake horsepower is, indeed, used in the water industry. I specify pumps for an engineering consulting firm and we use it all the time.


breakofday - I think people in the US are moreover concerned with how much power something has rather than technicalities or abilities. That's a sad thing to say, but horsepower is a major concern for many people and not just professional racers anymore. With the main focus of horsepower being the higher it is, the more work your engine can do, one can easily understand the obsession and need for a high performing engine with lots of horsepower.


I don't think the term "brake horsepower" is used very much in the States. All I've ever heard is Horsepower. But overseas they seem to exclusively use brake horsepower.

I guess it doesn't really matter anymore that the whole term "horsepower" actually came from comparing the power of an engine to the power of draft horses.

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