Find the horsepower behind the numbers.
Work out engine horsepower three ways: from torque and RPM, from vehicle weight and quarter-mile trap speed, or from weight and elapsed time. See the answer in horsepower, kilowatts, and metric horsepower at once.
The engine
Used only for the power-to-weight ratio. The weight and trap or ET methods fill this in for you.
HP = torque x RPM / 5,252. Torque times how fast the engine spins gives the rate of work.
What the numbers say
Horsepower across the rev range
HP vs RPM at your torque figure
Power scorecard
Horsepower at each RPM
At a fixed torque figure, horsepower climbs in a straight line with engine speed.
Horsepower, explained
The Horsepower Formula
Horsepower is calculated as HP = (Torque x RPM) / 5,252. The constant 5,252 comes from the relationship between rotational and linear work. At exactly 5,252 RPM, horsepower and torque are always equal.
Torque vs Horsepower
Torque is the twisting force the engine produces, measured in pound-feet. Horsepower is the rate at which work is done, combining torque and speed. Torque determines acceleration from a stop, while horsepower determines top speed and sustained performance.
HP, kW, and Metric HP
One mechanical horsepower equals 0.7457 kilowatts (kW). One metric horsepower (PS) equals 0.9863 mechanical HP. European cars often list power in kW or PS. This calculator converts between all three units.
Horsepower at the Wheels vs Engine
Brake horsepower (BHP) is measured at the engine output. Wheel horsepower (WHP) is measured at the wheels after drivetrain losses. Automatic transmissions lose about 15-20% and manual transmissions lose about 10-15% of engine power.
Common questions
What is the difference between HP and BHP?
BHP (brake horsepower) is the power measured at the engine crankshaft. HP (horsepower) is a general term. WHP (wheel horsepower) is measured at the wheels. Due to drivetrain losses, WHP is always lower than BHP.
Why is 5,252 RPM significant?
At exactly 5,252 RPM, horsepower and torque values are always equal. Below this RPM, torque is higher than horsepower. Above it, horsepower exceeds torque. This is a mathematical fact of the HP = (T x RPM) / 5,252 formula.
How do I convert horsepower to kilowatts?
Multiply horsepower by 0.7457 to get kilowatts. For example, 300 HP equals about 224 kW. Conversely, multiply kW by 1.341 to convert to HP. Electric vehicle specifications typically use kW.
What is a good horsepower for a car?
Economy cars have 100-150 HP, mid-size sedans 180-250 HP, performance sedans 300-400 HP, and sports cars 400+ HP. Horsepower needs depend on vehicle weight, intended use, and personal preference.
Estimates for planning and comparison only. Torque and RPM give crank horsepower; drag-strip trap-speed and ET formulas (Fox and Hale) are rough estimates that vary with traction, air density, drivetrain losses, and driver skill. Measure on a dyno for a true figure.