What this calculator does
A quarter mile is a fixed distance: 402.336 metres, or 0.402336 km, and 1,320 feet, the standard length of a drag strip. That part never changes. What people usually mean by a "quarter mile calculator" is an estimate of how fast a given vehicle would cover that distance: its elapsed time (ET) and trap speed, the speed at the finish line.
This calculator estimates ET and trap speed from a widely used empirical formula based on a vehicle's weight and power. It is a rough approximation, not a guarantee: real results depend heavily on tyres, gearing, launch technique, driver skill, aerodynamics and track conditions, none of which this formula accounts for. Treat the numbers as a ballpark, not a promise.
The formula
Elapsed time (in seconds) is approximated as 5.825 × (weight in pounds ÷ power in horsepower)^(1/3). Trap speed (in mph) is approximated as 234 × (power in horsepower ÷ weight in pounds)^(1/3). Both come from the same underlying weight-to-power relationship and are a long-standing rule of thumb in drag racing, not a law of physics.
| Term | Meaning |
|---|---|
| Elapsed time (ET) | The time taken to cover the quarter mile from a standing start, in seconds. |
| Trap speed | The vehicle's speed at the finish line (the end of the quarter mile), in mph. |
| Weight-to-power ratio | Vehicle weight divided by engine power, in lb per hp; a lower ratio generally means quicker acceleration. |
The inputs explained
| Field | What to enter |
|---|---|
| Vehicle weight (with driver) (lb) | The vehicle's total weight including the driver, in pounds. |
| Engine power (hp) | The engine's power output, in horsepower, at the wheels or at the crank depending on which figure you are working with (results shift if you switch between the two). |
When to use it
Ballparking a build's performance
Before dyno testing or an actual track run, plugging in an estimated weight and power figure gives a rough idea of what ET and trap speed to expect from a modification.
Comparing the effect of weight reduction versus more power
Running the same vehicle through both a lighter weight and a higher power figure shows, side by side, which change moves the estimated ET more for the same relative effort.
Converting the fixed distance itself
For the "quarter mile in km" question rather than a performance estimate, the answer is fixed regardless of any vehicle: 0.402336 km, 402.336 m, or 1,320 feet.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How estimated ET and trap speed change with vehicle weight
A fixed 300 hp, across a range of vehicle weights.
| Vehicle weight | Estimated elapsed time | Estimated trap speed |
|---|---|---|
| 2,400 lb | 11.65 s | 117.0 mph |
| 2,800 lb | 12.26 s | 111.1 mph |
| 3,200 lb | 12.82 s | 106.3 mph |
| 3,600 lb | 13.34 s | 102.2 mph |
| 4,000 lb | 13.81 s | 98.7 mph |
| 4,500 lb | 14.37 s | 94.9 mph |
How estimated ET and trap speed change with engine power
A fixed 3,200 lb vehicle weight, across a range of engine power figures.
| Engine power | Estimated elapsed time | Estimated trap speed |
|---|---|---|
| 150 hp | 16.16 s | 84.4 mph |
| 200 hp | 14.68 s | 92.9 mph |
| 300 hp | 12.82 s | 106.3 mph |
| 400 hp | 11.65 s | 117.0 mph |
| 500 hp | 10.81 s | 126.0 mph |
| 700 hp | 9.67 s | 141.0 mph |
Questions
How far is a quarter mile?
Exactly 402.336 metres, 0.402336 km, or 1,320 feet. This is a fixed length, the standard distance of a drag strip, and does not depend on the vehicle.
Quarter mile in km, what is it exactly?
0.402336 km, since a quarter mile is defined as a quarter of a statute mile (1,609.344 m), and 1,609.344 ÷ 4 = 402.336 m.
How accurate are these quarter mile times?
They are rough estimates from a widely used weight-to-power formula, not a measurement. Real elapsed times vary with tyres, gearing, launch technique, driver skill, aerodynamics, altitude and track surface, any of which can shift actual results well away from this estimate.
Should I use crank horsepower or wheel horsepower?
Either can be used, but be consistent about which one you enter, since drivetrain losses mean wheel horsepower is typically noticeably lower than crank horsepower for the same engine. Using wheel horsepower generally gives a more realistic (slightly slower) estimate.
For the underlying weight-to-power relationship applied to other speed and acceleration problems, see the physics calculators elsewhere on the site.