Brake Horsepower Calculator
Calculate brake horsepower (BHP) and see how it differs from wheel horsepower.
Brake horsepower (BHP) is the power measured at the engine's crankshaft, before any losses through the drivetrain. It's the figure manufacturers advertise, and it's calculated the same way as any crank horsepower.
Brake Horsepower Formula
The term "brake" comes from the Prony brake, an early device that measured engine power by applying a braking load. Today BHP means crank horsepower measured with all accessories — it's effectively the same as the SAE net figure quoted in brochures.
How to Use This Calculator
- Enter torque in lb-ft and RPM.
- Read BHP, with an estimated wheel horsepower shown below.
Worked Example
To work between crank and wheel figures, use the wheel horsepower calculator, and read wheel HP vs crank HP for the full explanation.
BHP vs Wheel Horsepower
Brake horsepower is measured at the crankshaft on an engine dyno, before the transmission, driveshaft, and differential take their cut. Wheel horsepower (WHP), measured on a chassis dyno, is always lower by the drivetrain loss — typically 10–25% depending on layout. When you see a manufacturer's power figure, it's BHP (specifically SAE net); when a tuner quotes a dyno number, it's usually WHP.
Why It's Called "Brake" Horsepower
The name comes from the Prony brake, a 19th-century device that measured an engine's output by applying a friction brake to its shaft and recording the force needed to slow it. The principle — loading the engine and measuring the work it does against that load — is still how modern dynos work, so "brake horsepower" remains the term for crank-measured power.
BHP and Estimated WHP (at 5,500 RPM)
| Torque (lb-ft) | BHP | ~WHP (15% loss) |
|---|---|---|
| 300 | 314 | 267 |
| 350 | 367 | 312 |
| 450 | 471 | 401 |
Frequently Asked Questions
Brake horsepower is the power measured at the engine's crankshaft before drivetrain losses, calculated as (torque × RPM) ÷ 5252. It's the figure manufacturers usually advertise.
In practice they're used interchangeably for crank power. BHP specifically refers to power measured at the crank with a braking load, while 'HP' is the general unit.
No. BHP is measured at the crank; wheel horsepower is lower because the drivetrain absorbs 10–25% of the power before it reaches the road.
From the Prony brake, an early instrument that measured engine output by applying a known braking force to the spinning shaft.
Multiply BHP by (1 minus the drivetrain loss). For a typical RWD car with 15% loss, multiply by 0.85.