Horsepower Trap Speed Calculator

Enter the horsepower, weight, and trap speed into the calculator to determine the missing variable.

Horsepower Trap Speed Formula

The following formula is used to calculate the trap speed for a given horsepower and weight.

TS = 234 * (HP / W)^{(1/3)}

Variables:

TS is the trap speed in miles per hour (mph)
HP is the horsepower
W is the weight in pounds (lbs)

To calculate the trap speed, multiply 234 by the cube root of the ratio of horsepower to weight.

What is a Horsepower Trap Speed?

Horsepower trap speed is a measure used in drag racing to estimate the power output of a vehicle based on its weight and the speed it achieves at the end of a quarter-mile run. The trap speed is the speed of the vehicle as it crosses the finish line. This measurement helps in understanding the vehicle’s performance and efficiency in converting horsepower into speed. Higher trap speeds generally indicate more powerful and efficient vehicles.

How to Calculate Horsepower Trap Speed?

The following steps outline how to calculate the Horsepower Trap Speed.

First, determine the horsepower (HP) of the vehicle.
Next, determine the weight (W) of the vehicle in pounds.
Next, calculate the trap speed (TS) using the formula TS = 234 * (HP / W)^(1/3).
Finally, calculate the Horsepower Trap Speed.
After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem :

Use the following variables as an example problem to test your knowledge.

Horsepower (HP) = 400

Weight (W) = 3200 lbs

Follow-Up Calculations

If your trap-speed result says a 3,600-pound car is making about 450 hp at the crank, you can check the wheel horsepower to estimate what a dyno would show after drivetrain losses. With a typical 15% loss, that same setup lands near 383 whp, which is often the number people compare when they talk about track performance.

If the trap-speed calculator puts your car at 450 hp but your chassis dyno shows 390 whp, you can estimate drivetrain loss and see that the gap is about 13%. That’s a useful reality check because a manual transmission, rear differential, and tires can each absorb a meaningful amount of power before it reaches the pavement.

A 450 hp trap-speed estimate at 6,000 rpm works out to about 394 lb-ft at the engine, and gearing can multiply that into several thousand pound-feet at the tires. If you want to estimate the wheel torque, it helps you understand why a car can feel much stronger in first gear than the horsepower number alone suggests.