Engine Horsepower Calculator

Estimate HP from 1/4-mile ET and vehicle weight (Fox formula sketch).

Engine Horsepower Calculator helps you estimate HP from 1/4-mile ET and vehicle weight (Fox formula sketch). Enter weight and quarter-mile time, review the breakdown, and use the guidance below to understand what the number means — and what it does not. What the Engine Horsepower calculator does Engine Horsepower Calculator is built for everyday questions — shopping, home, travel, hobbies, and tech. Estimate HP from 1/4-mile ET and vehicle weight (Fox formula sketch). You enter weight and quarter-mile time, then Simple Calculators computes the result instantly. Defaults are chosen to be easy to read — change any field to match your situation. How the math works Pick Units, then enter the car’s Weight including the driver (pounds or kilograms) and its Quarter-mile time in seconds — the elapsed time, or ET, from the start line to the finish. Kilograms are converted to pounds. Horsepower ≈ weight ÷ (quarter-mile time ÷ 5.825)³, where 5.825 is a constant from drag-racing experience. It assumes a good launch and normal track conditions, so treat it as an estimate. The formula: HP ≈ weight (lb) ÷ (quarter-mile time ÷ 5.825)³. Time is in seconds. Heavier cars need more power to run the sa…