Quarter Mile Calculator

Given a vehicle's power and weight, you can use this quarter-mile calculator to estimate the elapsed time and final speed over a 1/4-mile distance.

Estimated elapsed time13.547 secondsHuntington's empirical relation — a fitted rule, not a derivation

Estimated trap speed104.01 mph167.4 km/h

Power320 hp238.624 kW

Power to weight220.69 hp per tonne164.57 W/kg

Weight to power9.99 lb per hp

Power for one second quicker403 hpthe cube root means gains get expensive fast

At twice the power10.752 sonly 20.6% quicker — doubling power buys a cube root of improvement

At 100 kg less mass13.228 smass and power enter the same way, inverted — shedding weight and adding power are interchangeable

Theoretical floor at constant full power2.211 sfrom energy alone, ignoring traction, gearing and drag — always optimistic, and the gap to the estimate above is what real drivetrains lose

Traction-limited floor at 1.0 g9.058 sno amount of power beats this without more grip — a street tyre cannot reach it, a drag slick can exceed it

The formula

ET ≈ 6.290 × (weight ÷ power)^⅓; trap speed ≈ 224 × (power ÷ weight)^⅓

A fitted rule, and why it works

The relations here are Roger Huntington's, fitted to observed drag-strip results rather than derived. They work remarkably well across a wide range of cars because the underlying physics really is close to a cube-root law: over a fixed distance, time scales as the cube root of weight over power.

That cube root is the important lesson. Doubling power makes a car only about 21% quicker over the quarter mile, and buying a second off a 13-second run costs far more power than buying one off an 18-second run. Weight and power enter identically and inverted, so removing 10% of the mass is worth as much as adding 11% more power — usually much cheaper.

Two floors are shown for contrast. The energy floor assumes full power from a standstill, which no real car achieves; the traction floor assumes the tyres can hold 1 g and no more. Real times sit above both, and where they sit depends on gearing, launch and how quickly the engine reaches its power band. The estimate is worth perhaps a couple of tenths of a second, not three decimal places.