Drag Racing ET Calculator

The Huntington formulas (ET = 5.825·(weight/hp)^(1/3) and MPH = 234·(hp/weight)^(1/3)) are empirical fits built from decades of real quarter-mile results, so they capture how weight and power translate to elapsed time and trap speed for typical cars without needing gearing, tire, or aerodynamic data most users don't have. They trade precision for simplicity — accurate for street and race cars in normal ranges, less reliable for extreme outliers like dragsters.

It starts from the entered track altitude and adds roughly 60 feet of 'effective' altitude for every 10°F the air temperature sits above the 59°F standard reference, since warm air is less dense and behaves like being at a higher elevation. This simplified estimate skips humidity and barometric pressure, which also affect real density altitude, but it captures the dominant temperature effect.

A naturally aspirated engine makes less power in thinner, warmer air, so the calculator reduces your entered horsepower by about 3% for every 1,000 feet of estimated density altitude before plugging it into the Huntington formulas. This means the same car will show a slower predicted ET at a high-altitude or hot track than at sea level on a cool day, even with identical horsepower entered.

It's a widely used rule of thumb in drag racing rather than something derived from this calculator's own physics — eighth-mile times consistently run close to 63.2% of the corresponding quarter-mile ET across a wide range of vehicles, so the calculator applies that fixed ratio directly to the predicted quarter-mile figure.