drag racing
Quarter-mile ET
Explore empirical quarter-mile elapsed-time and trap-speed estimates from race-ready weight and engine horsepower, with visible model coefficients.
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DRAG RACING CALCULATORET to Horsepower
ET to Horsepower
Calculator
Invert an empirical quarter-mile ET model to estimate effective engine horsepower from time and race-ready weight. This is not a dynamometer measurement.
Your setup
lb
Include the driver, fuel and equipment.s
Range: 1.00–60.00 sYour results
CalculatedModel-implied power366.01hp
Metric power272.93kW
The output is the power implied by this model, not independently measured crank or wheel power.
READ THE ASSUMPTIONS
Traction-limited or interrupted runs can greatly understate power. Do not use eighth-mile times.
THE FORMULA
How the calculation works
Follow the formula and keep the input units consistent at every step.
estimated HP = W_lb / (ET / 5.825)³- Enter quarter-mile ET and race-ready weight.
- Divide ET by 5.825 and cube it.
- Divide weight in pounds by that result.
A Worked Example
3,200 lb and 11.65 s give ET/5.825 = 2 and estimated power = 3,200 / 8 = 400 hp.
What Your Result Means
The output is the power implied by this model, not independently measured crank or wheel power.
Assumptions & Limitations
Traction-limited or interrupted runs can greatly understate power. Do not use eighth-mile times.
Common Mistakes
Reaction time is excluded from elapsed time. Do not add it to the time-slip ET.
Questions about this calculation
Which values should I enter?
Enter quarter-mile ET and race-ready weight. Reaction time is excluded from elapsed time. Do not add it to the time-slip ET.
How should I interpret the result’s precision?
Displayed results are rounded for readability. Intermediate calculations retain floating-point precision; extra displayed decimals do not improve your input accuracy.
Can I use metric units?
Yes. Select Metric above the calculator to convert your inputs. Results always state their units. Tire-size designations keep their conventional mm and inch units.
What are the main limitations?
Traction-limited or interrupted runs can greatly understate power. Do not use eighth-mile times.
Method, sources & relevant guides
Hale coefficient model: ET constant 5.825 and speed constant 234. Lucius documents the formulas and compares them with road-test data. These are empirical relationships, not physical laws or calibrated vehicle predictions.
Jeff Lucius / Stealth 316 — Quarter-mile formulas and original regression analysisMethod documentation updated October 18, 2026. Independent professional review has not been claimed. Read the calculation and review policy.