Engine Horsepower Calculator

Quarter-mile performance and weight — an empirical horsepower estimate.

lb
mph

Both are empirical drag-strip formulas, not precise physics — useful for rough comparisons, not certified power figures. Always measure elapsed time and trap speed in a safe, legal setting like a drag strip.

Estimated horsepower
273.2 HP

The trap-speed method tends to be more stable since it depends mainly on the energy delivered through the run, while the elapsed-time method is more sensitive to launch traction and shifting.

A worked example

A 3,750 lb vehicle crossing the quarter-mile finish line at 100 mph trap speed estimates to about 292.7 horsepower.

Frequently asked questions

Which method should I trust more — ET or trap speed?

Trap speed is generally considered more reliable since it reflects the energy delivered across the whole run; elapsed time is more sensitive to launch traction, reaction time, and shifting, which can throw off the estimate even when the engine's actual power hasn't changed.

Why does this only work for a quarter mile?

Both formulas are empirical — derived by fitting curves to large amounts of real quarter-mile (1,320 ft) drag strip data, not from first-principles physics. They're calibrated specifically for that distance and don't translate directly to other distances.

Is this estimate the same as a dyno result?

No — it's a rough estimate using only weight and performance data, not a direct power measurement. A dyno measures actual power output and is considerably more precise, though also more involved to access.

Quarter-mile testing should only be done in safe, legal venues such as sanctioned drag strips — never on public roads.