Works in pounds, kilograms, hp, kW and PS
1/4 Mile Calculator
Most online calculators assume pounds and horsepower. This one lets you switch freely between lb and kg, and between hp, kW and PS, so a spec sheet from anywhere in the world can go straight in.
- 1/8-mile ET
- 8.01 sec
- 1/8-mile speed
- 87.3 mph
- Trap speed
- 175.6 km/h
- Weight per hp
- 9.86 lb/hp
- Conservative ET (Huntington)
- 13.49 sec
- Conservative trap (Huntington)
- 104.4 mph
Using the 1/4 mile calculator with metric specs
European and Japanese specifications usually give kerb weight in kilograms and output in kW or PS. Enter them as they are: the calculator converts everything to pounds and mechanical horsepower before applying the formula, then shows the result in seconds and both mph and km/h.
The preset above is a 1,500 kg car with 250 kW (about 335 hp), which works out to roughly 12.49 s at 109.1 mph. Remember to add the driver to the manufacturer’s kerb weight.
The estimate uses the widely published Patrick Hale equations: ET = 5.825 × (weight ÷ hp)1/3 and MPH = 234 × (hp ÷ weight)1/3, with weight in pounds and hp measured at the crank. They are documented, along with the more conservative Huntington (6.290 / 224) and Fox constants, in Stealth316’s horsepower / ET / MPH calculator notes. See the full formulas and sources page.
Quick unit conversions that matter
| From | To | Multiply by |
|---|---|---|
| kilograms | pounds | 2.2046 |
| kilowatts | mechanical hp | 1.3410 |
| PS (metric hp) | mechanical hp | 0.9863 |
| mph | km/h | 1.6093 |
PS and mechanical horsepower differ by about 1.4%, which is small but worth getting right on a close bracket.
Kerb weight versus race weight
Brochure weights are often quoted without a driver and sometimes with a partly filled tank. Add about 75 kg (165 lb) for a driver and a fuel allowance when you can. A lighter number flatters the car by a tenth or two.
Frequently asked questions
How do I convert kW to hp for a quarter mile estimate?
Multiply kilowatts by 1.341 for mechanical horsepower. The calculator does this automatically when you pick kW in the power box.
Is a 1/4 mile exactly 400 meters?
No. A quarter mile is 1,320 ft or 402.336 m, so it is slightly longer than 400 m. See how many feet are in a quarter mile.
Why is my result different from another calculator?
Different sites use different constants. This tool shows the popular Hale constants as the main estimate and the more conservative Huntington figures as a range.
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