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Engine Horsepower Calculator

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

About the Engine Horsepower 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.

How the Engine Horsepower Calculator works

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 the Engine Horsepower Calculator

  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 for the Engine Horsepower Calculator

  • 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 used by the Engine Horsepower Calculator

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

Example: Engine Horsepower Calculator

A 3,200 lb car running a 13.5s quarter mile at 100 mph trap speed

  • Weight: 3,200 lb
  • Elapsed time: 13.5 s
  • Trap speed: 100 mph

Result: From ET ≈ 257.1 HP; from trap speed ≈ 249.7 HP

From ET: 3,200 ÷ (13.5 ÷ 5.825)³ ≈ 257.1 HP. From trap speed: 3,200 × (100 ÷ 234)³ ≈ 249.7 HP — the two estimates naturally differ since they use different inputs.

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