🏎️ Horsepower Calculator
Estimate your vehicle's horsepower from quarter mile trap speed or elapsed time using standard drag racing formulas.
Vehicle & Run Data
Your Result
These formulas give rough estimates commonly used in drag racing to ballpark horsepower from time-slip data. They are not a substitute for a dyno test and don't account for aerodynamics, traction, or driver skill.
How the Horsepower Calculator Works
Drag racers have long used simplified formulas based on quarter-mile trap speed or elapsed time (ET) to estimate flywheel horsepower without needing a dyno. Both methods use vehicle weight as a key input.
Formulas
Elapsed Time Method: HP = Weight (lb) / (ET (seconds) / 6.290)³
Worked Example
For a 3,400 lb vehicle with a quarter-mile trap speed of 95 mph, the trap speed formula gives HP = 3,400 × (95 ÷ 234)³ ≈ 228 horsepower. That works out to a weight-to-power ratio of about 14.94 lb/hp — a useful number for comparing cars of different weights and power levels.
Frequently Asked Questions
How accurate is the quarter mile horsepower formula?
These formulas provide a rough estimate, typically within 5-15% of actual dyno-measured horsepower. Track conditions, tire grip, aerodynamics, and driving technique all affect the result.
Which method is more reliable, trap speed or ET?
The trap speed method is generally considered more reliable because elapsed time is more sensitive to launch technique and traction, while trap speed better reflects the car's power near the end of the run.
Should I use curb weight or weight with driver?
Use the actual weight of the vehicle as it was during the run, including the driver, fuel, and any passengers, for the most accurate estimate.