Trap Speed Horsepower Calculator
Estimate horsepower from quarter-mile trap speed and vehicle weight.
Trap speed — the MPH recorded at the end of a quarter-mile run — is one of the most reliable ways to estimate horsepower from a timeslip, because it reflects sustained power rather than launch technique.
Trap Speed HP Formula
This is one of Patrick Hale's widely used drag-racing equations. Because trap speed reflects how much power the car carries to the finish line, it's less sensitive to a poor launch than elapsed time — making it the preferred horsepower estimator among racers.
How to Use This Calculator
- Enter trap speed in MPH from your timeslip.
- Enter race weight including driver.
- Read the estimated horsepower.
Worked Example
Compare against an ET-based estimate with the HP from ET calculator, or predict a full run with the quarter mile calculator.
Frequently Asked Questions
Use HP = Weight × (MPH ÷ 234)³, where weight is in pounds including driver and MPH is the quarter-mile trap speed.
Trap speed reflects sustained power at the finish, while ET is heavily affected by launch quality and traction. So trap speed correlates more directly with horsepower.
Typically within 5–10% for a car with reasonable aerodynamics and weight. Very heavy or unusually shaped vehicles show more error.
Race weight — the car as it ran, including fuel and driver. Using an empty curb weight underestimates horsepower.
The estimate approximates flywheel (crank) horsepower, since it's based on the power needed to accelerate the whole vehicle.