Quarter-Mile ET Calculator

A stock economy car runs 15-17 seconds. A sport sedan or hot hatch hits 13-14 seconds. A dedicated muscle car or sports car is 11-12 seconds. Purpose-built supercars like the Porsche 911 Turbo S run under 10 seconds. Under 10 seconds at the street is supercar territory; under 8 seconds requires serious drag-specific preparation and slicks.

Trap speed is the vehicle's velocity at the finish line - the speed recorded by timing lights at the 1,320-foot mark. It is a direct reflection of the car's power-to-weight ratio because it measures the end-state velocity after a full-length acceleration run. Unlike ET, it is relatively insensitive to launch quality, reaction time, or how quickly the car hooks up - making it a better diagnostic tool for engine power.

The formula was derived from four-wheeled vehicles and may not be accurate for motorcycles, which have very different power-to-weight ratios, launch dynamics (wheelie management), and aerodynamics. Purpose-built drag bikes with 200+ hp at 400-500 lb can run 6-7 second quarter miles, well outside what the formula predicts.

Higher altitude means less air density, which reduces power in naturally aspirated engines by approximately 3% per 1,000 feet of elevation. At Denver (5,280 ft), an engine makes about 15% less power than at sea level. This lengthens ET and lowers trap speed predictably. Turbocharged and supercharged engines are less affected since boost compensates for lower intake density.