Quarter Mile & 0–60 Calculator

How the estimate works

Quarter-mile ET and trap speed use the Huntington drag-racing relationships, which tie elapsed time and trap speed to power-to-weight and nothing else:

ET = 5.825 × (lb ÷ hp)⅓  ·  trap = 234 × (hp ÷ lb)⅓

Those cube roots are why chasing power gets expensive. To halve your ET you would need eight times the power — and why 100 kg out of the car is worth more than it looks on a spec sheet. 0–60 is estimated from the same ratio and adjusted for drivetrain: AWD hooks up and launches hardest, FWD unloads the driven wheels and spins soonest.

A worked example, and the numbers the tool gives for it: 300 hp in a 1,450 kg car is 10.7 lb/hp, which lands on a 12.82 s quarter at a 106 mph trap, and 5.9 s to 60 mph on a rear-drive launch.

Eighth-mile to quarter-mile

Plenty of strips only run an eighth of a mile — 660 feet — because the shutdown area a quarter needs is expensive real estate. If your slip says 1/8, two conversions have been in use for decades and they are close enough to trust:

¼ ET ≈ ⅛ ET × 1.55  ·  ¼ trap ≈ ⅛ trap × 1.25

The same 300 hp, 1,450 kg car that runs a 12.82 s quarter at 106 mph goes through the eighth in 8.27 s at 85 mph. The relationship holds because the second half of a quarter is run on the same power-to-weight the first half was — the car is simply still accelerating, more slowly, against more drag.

Three things break the rule, and all three break it in a predictable direction:

• A bad launch flatters the conversion. A car that spins for the first 60 feet loses most of that time in the eighth and then pulls cleanly to the quarter, so ×1.55 will over-estimate its quarter-mile ET.
• A slow-spooling turbo does the opposite. If boost only arrives properly halfway down the track, the eighth-mile time is not representative of what the car does afterwards, and the real quarter comes in quicker than ×1.55.
• Running out of gear or aero hurts the far end. A car that hits the limiter before the lights, or is simply too draggy to keep pulling, will be worse than the rule suggests. That is the same drag wall the top speed calculator describes.

For comparing two runs of the same car, the conversion is very reliable. For comparing two different cars, use the trap speeds: trap is the one figure that barely cares how well either of them launched.

Quarter-mile reference chart

Both tables are generated by running the calculator above, so a row here cannot disagree with the tool.

ET, trap speed and 0–60 by power-to-weight

Elapsed time and trap speed depend on nothing but the power-to-weight ratio, so one row covers every car that shares it. 0–60 is shown for a rear-drive launch.

Quarter-mile ET by power and weight

The same maths as a lookup grid, in the units you already have. Weight is with driver and fuel.

Eighth-mile to quarter-mile

Find your eighth-mile slip on the left. Each row is the calculator solved backwards for the power that produces that time, then read across — so the conversion is the tool’s own, not a separate rule of thumb.

ET or trap speed — which one tells the truth?

They measure different things, and this is the single most useful idea on the page.

• Trap speed measures the engine. It is the speed at the end of the quarter, by which point the launch is long forgotten. Trap barely moves with traction, so it is the honest read on how much power the car actually makes.
• ET measures the whole run. Elapsed time includes the launch, the 60-foot, every shift and every wheelspin — so ET rewards a driver and a set of tyres as much as an engine.

That is why two cars can trap identically and finish a tenth apart, and why a tuner asks for your trap speed rather than your ET. If you already have a time slip, work backwards from it with the trap speed horsepower calculator — the same relationship, solved for power.

What the 60-foot time does to your ET

The first 60 feet is where a quarter-mile run is won or lost. A rough rule drag racers use: every 0.1 s off your 60-foot is worth roughly 0.2 s of ET, and that gain is nearly free — it costs tyre pressure and launch technique, not money.

Rough 60-foot benchmarks for a street car: 2.2 s or worse means you are spinning or bogging; 1.9–2.0 s is a decent street-tyre launch; 1.7 s needs a sticky tyre and a car that squats. This calculator assumes a competent launch for the drivetrain you pick — it cannot see your tyres.

Why the strip disagrees with the estimate

The formulas describe a car that puts its power down. Real runs differ, and almost always in the same directions:

• Traction. The biggest single variable. Street tyres on a cold, unprepped surface can cost half a second of ET that no amount of power buys back.
• Gearing. A car that has to shift right at the stripe, or that runs out of gear before it, loses time the formula never sees. Check yours with the gear ratio calculator.
• Air. A hot, humid, high day makes less power and more ET. Density altitude of 3,000 ft is worth several tenths — the density altitude calculator gives the number for your day.
• Which power figure you typed. Crank power matches these formulas. Wheel power does not, and will read optimistically fast.
• Weight. Kerb weight is not race weight. Driver, fuel, and whatever is still in the boot all count.

Expect the estimate to be close on a well-prepped car and optimistic on a stock one. Treat it as the number your car should run, and the difference as the size of your traction problem.

FAQ

Where to go next

Power-to-weight is the ratio all of this rests on — see it directly with the power-to-weight calculator. Working backwards from a real time slip is the trap speed calculator. And if you would rather run the quarter than calculate it, your saved car will launch down a simulated strip in Drag Race.