Quarter mile time calculator
Quarter mile elapsed time and trap speed from engine power and vehicle mass.
Fill in the fields and the result will appear here automatically.
A conditional quarter-mile time and trap-speed estimate from mass and power. It uses the inherited empirical coefficient preset 5.825 and 234; the original calibration has not been verified, so no accuracy range is claimed and the result does not replace a timed run. Enter mechanical hp and kg including the driver and actual load. Traction, shifting, aerodynamics and track conditions are not modelled.
How it works
Formula and logic
W = kg·2.2046226218 and P is mechanical hp. ET = 5.825·∛(W/P) seconds; V = 234·∛(P/W) mph; km/h = mph·1.609344. A quarter of an international mile is 402.336 m. Both inputs are positive and all output quantities must be finite and nonzero. The model makes no crankshaft-to-wheel power correction.
Example
150 hp and 1300 kg give 15.6 seconds and about 141 km/h at the traps.
Fields and units
- Power, hp — hp
- Kerb mass with driver, kg — kg
How to use
- — Enter positive power in mechanical hp; metric PS is a different unit.
- — Enter kg including the driver and actual load without counting them twice.
- — Keep the power definition consistent between scenarios; read time and speed as conditional estimates with no claimed accuracy.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- NIST SP 811 B8: units and metric PS versus mechanical hp; tabulated factors are rounded
- Limitation
- Enter positive power in mechanical hp; metric PS is a different unit. Keep the power definition consistent between scenarios; read time and speed as conditional estimates with no claimed accuracy.
FAQ
Why is there no traction or gearing in the formula?
That is a limit of the two-input approximation. It cannot assess launch, wheelspin, gearing, drag or surface; cars with the same power-to-mass ratio can produce different runs.
How accurate is it?
There is no verified error range for this preset. It promises neither agreement within 0.1 seconds nor an “ideal” time. Validate it against actual runs with comparable mass, power and conditions.
Which power figure should I use?
The field uses mechanical hp, not metric PS. There is no universal wheel-to-crank correction, and without verified calibration neither basis can be declared correct for every car. Keep the power definition consistent across comparisons.
How should I interpret trap speed?
Here speed is another output of the same power-to-mass ratio. Real time and speed reflect different aspects of a run, but the calculator does not establish that one is superior or recover true power from it.