Calculators
Engine Horsepower Calculator
Estimate horsepower from the quarter mile.
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About the Engine Horsepower Calculator
Estimate an engine's power from track data. Enter the vehicle's weight and its quarter-mile trap speed and the calculator estimates horsepower using the well-known Fox formula: hp = weight × (speed ÷ 234)³. It's a fun, surprisingly accurate way to gauge real-world power.
How to use the Engine Horsepower Calculator
- 01Enter your vehicle weight and quarter-mile trap speed.
- 02Read the result instantly — it recalculates as you type.
- 03Adjust the numbers to model different scenarios.
Frequently asked questions
How accurate is the trap-speed method?
It's a good estimate for stock-ish cars — the Fox formula ties trap speed and weight to power. Aerodynamics and drivetrain loss add variance.
What is trap speed?
Your speed as you cross the quarter-mile finish line. It reflects power-to-weight better than elapsed time alone.