Quarter Mile ET Calculator
Estimate quarter-mile elapsed time and trap speed from vehicle weight and horsepower.
Estimated quarter-mile ET
12.82 s
At a power-to-weight of 10.7 lb per hp, expect a trap speed around 106.3 mph. Real times swing with traction, gearing, and the driver.
Elapsed time
12.82 s
Trap speed
106.3 mph
How it works
Drag racers noticed decades ago that a car's quarter-mile time tracks its power-to-weight ratio remarkably well. This tool uses the classic empirical formulas: elapsed time equals 5.825 times the cube root of weight divided by horsepower, and trap speed equals 234 times the cube root of horsepower divided by weight.
Enter the car's weight in pounds (with driver and fuel, ideally) and its horsepower at the wheels or crank. A 3,200-pound car with 300 horsepower lands near 12.9 seconds at roughly 106 mph — right where a quick street car tends to run.
These are estimates from power and weight alone, so they assume a car that hooks up and launches cleanly. Traction, tires, gearing, aerodynamics, and driver skill all move the real number. Use it to compare builds and set expectations, not as a substitute for a timeslip.
Frequently asked questions
Should I use crank or wheel horsepower?
The formulas were fit to real cars, so wheel horsepower usually gives a truer time since that's the power actually reaching the ground. If all you have is a crank figure, expect the real ET to be a touch slower than the estimate.
Why is my actual time slower than the estimate?
The formula assumes a clean launch and full traction. Wheelspin, a tall first gear, street tires, or a nose-heavy layout all cost time. Cars that can't put their power down early often trail their power-to-weight prediction.
What weight should I enter?
Use race weight — the car as it runs, plus the driver and a realistic amount of fuel. Manufacturer curb weight leaves out the driver and can understate things, which makes the estimated ET look quicker than reality.