Quarter-Mile Horsepower Calculator
Convert a drag-strip time slip into an approximate power figure.
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Quarter-Mile Horsepower Calculator by TheCalcTools
How the Quarter-Mile Horsepower Calculator works
Enter the car’s weight including the driver and the time slip figures.
Two common empirical formulas estimate power from elapsed time and from trap speed.
Trap speed is usually the more reliable of the two, since it is less affected by launch.
The formula
Worked example
Using the default values shown in the calculator:
| Vehicle weight with driver (lb) | 3400 |
|---|---|
| Quarter-mile time (s) | 13.2 |
| Trap speed (mph) | 107 |
- From time: 3,400 ÷ (13.2 ÷ 5.825)³ = 292 hp.
- From speed: 3,400 × (107 ÷ 234)³ = 325 hp; average 309 hp.
Result:
| Horsepower from elapsed time | 292 |
|---|---|
| Horsepower from trap speed | 325 |
| Average estimate | 309 |
Frequently asked questions
Is this flywheel or wheel horsepower?
These empirical formulas approximate power at the wheels. Engine (flywheel) power is typically 10–20% higher.
How accurate are the results?
They are rough guides. Traction, gearing, air density and driver skill all change the numbers.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.