Quarter Mile Calculator
Enter flywheel horsepower and total vehicle weight to estimate your quarter-mile elapsed time and trap speed. These are well-known estimates, not a substitute for a real pass.
How to estimate a quarter-mile time
- Enter your engine horsepower at the flywheel.
- Enter total weight including the driver and fuel in pounds.
- Read the estimated elapsed time and trap speed.
Examples
300 hp, 3000 lb car
300 hp, 3000 lb
about 13.55 s at 103.97 mph
400 hp, 3200 lb car
400 hp, 3200 lb
about 12.58 s at 112.00 mph
Frequently asked questions
How accurate is this quarter-mile calculator?
It is an estimate. The Fox and Hale equations relate power and weight to elapsed time and trap speed, but real results depend on traction, gearing, aerodynamics, altitude and driver skill.
Should I use flywheel or wheel horsepower?
The classic equations assume flywheel horsepower. If you only have wheel horsepower, add roughly 15 percent for a typical drivetrain loss before entering it.
What weight should I enter?
Use the race weight: the full vehicle plus driver, fuel and anything else aboard during the pass. Heavier weight raises elapsed time and lowers trap speed.
Which is the better measure of engine power, ET or trap speed?
Trap speed is the cleaner indicator of power-to-weight because it depends less on launch traction. Elapsed time is strongly affected by how well the car hooks up off the line.
What are the equations used here?
Elapsed time equals 6.290 times the cube root of weight divided by horsepower. Trap speed equals 224 times the cube root of horsepower divided by weight. Power is in flywheel hp and weight in pounds.
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