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Engine Horsepower Calculator

Estimate an engine's horsepower from quarter-mile drag strip results — elapsed time or trap speed.

About this calculator

Estimate an engine's horsepower from quarter-mile drag strip results — elapsed time or trap speed — using the formulas racers have used for decades.

These formulas back-calculate horsepower from how a car actually performed on the strip, using its weight as the other input. They're estimates that assume a well-driven, properly-geared pass on a good track surface — real results vary with driver skill, tire grip, altitude, and weather, so treat the output as a ballpark figure rather than a dyno-accurate number.

How to use

  1. Enter the vehicle's total weight (including driver) in pounds.
  2. Enter the quarter-mile elapsed time in seconds, the trap speed in mph, or both.
  3. Press Calculate to see the estimated horsepower from each method provided.

Tips

  • The trap-speed method is generally considered more reliable than the elapsed-time method, since ET is more sensitive to launch technique and gearing.

Formula

From ET: HP = Weight ÷ (ET ÷ 5.825)³ From Trap Speed: HP = Weight × (Trap Speed ÷ 234)³