Empirical estimate from drag strip data — not as precise as a dyno reading, but a useful ballpark from time-slip data.
Free Engine Horsepower Calculator
This is a widely-used approximation (sometimes called the "Fox formula") relating trap speed and vehicle weight to horsepower at the wheels — it's an estimate derived from empirical drag racing data, not a precise physics derivation, so treat it as a ballpark figure rather than a dyno-accurate number.
Worked Example
Example: A 3,400 lb car with a 105 mph trap speed: HP = 3400 × (105/234)³ ≈ 306 HP.
Formula / Method
Horsepower = Weight (lb) × (Trap Speed (mph) / 234)³ — the empirical "Fox formula" used in drag racing.
Worked Example
Example: A 3,400 lb car with a 105 mph trap speed: HP = 3400 × (105/234)³ ≈ 306 HP.
Formula / Method
Horsepower = Weight (lb) × (Trap Speed (mph) / 234)³ — the empirical "Fox formula" used in drag racing.