Quarter Mile Horsepower Calculator
For decades, drag racers have estimated engine power from two easily measured numbers: the car's weight and its quarter mile elapsed time. This calculator applies the two best known empirical relations, the Huntington formula and the Hale formula, which were fitted to real drag strip results. Enter your race weight and elapsed time to get a horsepower estimate from each. These are estimates of power at the wheels under good traction, not laboratory crankshaft figures, so use them as a guide and compare against a dyno where possible.
Quarter mile horsepower formulas
Huntington: HP = weight / (ET / 5.825)^3
Hale: HP = weight / (ET / 6.290)^3
where weight is in pounds and ET is the quarter mile time in seconds
Both are empirical fits to drag strip data and estimate power at the wheels. They diverge at the extremes; quoting both gives a sensible range.
Worked example
A 3,400 lb car running a 13.5 second quarter mile. Huntington: 3,400 / (13.5 / 5.825)^3 = 273.13 horsepower. Hale: 3,400 / (13.5 / 6.290)^3 = 343.90 horsepower. The true figure typically falls within this band.
Quarter mile horsepower: frequently asked questions
How can horsepower be estimated from the quarter mile?
Drag racers use empirical relations that connect a vehicle's weight and quarter mile elapsed time (ET) to power at the wheels. The best known is the Huntington relation, horsepower equals weight divided by (ET / 5.825) cubed. These are observed fits to real strip data, not exact physics, so treat the output as an estimate of power at the wheels under good traction.
Why does weight matter so much?
Acceleration depends on power-to-weight ratio, so a heavier car needs more power to run the same elapsed time. The relation captures this: doubling weight at the same ET implies roughly double the horsepower. Use the car's actual race weight including driver and fuel for the most accurate estimate.
Is the elapsed time or trap speed method more reliable?
Trap speed (the speed at the end of the quarter) is generally considered a more reliable horsepower indicator than elapsed time, because ET is strongly affected by launch traction and reaction off the line, while trap speed reflects sustained power. This tool uses the ET method; our trap speed calculator uses the speed method.
Sources
- The Huntington (coefficient 5.825) and Hale (coefficient 6.290) elapsed-time relations are long-published empirical drag racing estimators. They are presented here as engineering estimates, not exact physics. Underlying SI units of mass and time follow NIST: NIST SI Units.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.