Quarter Mile Time Calculator
Estimate how fast your car will run the quarter mile based on its power-to-weight ratio. Used by drag racers and enthusiasts to benchmark performance or compare builds.
Last updated: September 2026
Formula below · 2 sources (nhtsa.gov, Wikipedia) · Updated Sep 2026
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About this calculator
The quarter-mile time calculator uses Patrick Hale's empirical drag-strip formula: ET = 5.825 × ∛(weight / horsepower), where ET is the elapsed time in seconds, weight is the vehicle's race weight in pounds (including the driver), and horsepower is the engine's rated output. Elapsed time grows with the cube root of the weight-to-power ratio, so halving the pounds per horsepower cuts ET by about 21%, not 29%. The constant 5.825 was fitted to a large sample of real drag-strip passes. The older Roger Huntington formula has the same cube-root form with a constant of 6.290, which gives slower times. Either one is a ballpark estimate that ignores launch technique, traction, gearing and aerodynamics.
How to use
Suppose your car weighs 3,200 lbs and produces 400 HP. Step 1: Divide weight by horsepower: 3,200 / 400 = 8. Step 2: Take the cube root: ∛8 = 2. Step 3: Multiply by 5.825: 2 × 5.825 = 11.65 seconds. So your estimated quarter-mile elapsed time is about 11.7 seconds. To improve this number, you can either reduce weight or increase horsepower — the calculator lets you experiment with both variables instantly.
Frequently asked questions
How accurate is the quarter-mile time formula based on horsepower and weight?
The formula gives a reasonable ballpark estimate, typically within 0.5–1 second of real-world results for street cars under normal conditions. It does not account for driver skill, launch RPM, tire grip, or transmission type, so modified or race-prepped vehicles may see larger deviations. It is best used as a comparative tool — for example, to see how much a weight reduction or power upgrade would theoretically improve your ET.
What does the 5.825 constant represent in the quarter-mile formula?
The constant 5.825 is an empirically derived correction factor calibrated against real drag-strip timing data from a wide range of vehicles. It essentially scales the power-to-weight ratio into a realistic elapsed-time estimate in seconds. Other versions of the cube-root formula use slightly different constants: Roger Huntington's 6.290 and Geoffrey Fox's 6.269 both give slower times. Hale's 5.825 is the most widely cited value for modern street and performance cars.
How can I use horsepower and weight to improve my quarter-mile time?
The formula shows that elapsed time decreases when you either increase horsepower or reduce vehicle weight — and both changes have an equal mathematical impact on the ratio. For example, adding 50 HP to a 3,000-lb, 350 HP car has the same effect as removing 375 lbs. In practice, weight reduction often provides better real-world gains because it also improves braking, handling, and launch traction simultaneously.