Horsepower from Trap Speed Calculator

Elapsed time is dominated by the first 60 feet: tires, suspension, converter and driver skill decide whether the same car runs 12.9 or 13.4. Trap speed integrates acceleration over the entire 1320 feet, where aerodynamics and power-to-weight have averaged out the launch drama — a car that bogs off the line and a car that launches hard arrive at the traps within a couple mph. Estimating power from ET needs traction assumptions; from trap speed it barely does.

For typical full-bodied cars it lands within ±5%: the exponent-3 form encodes that aerodynamic and rolling losses grow with speed. Variants exist — 230 to 237 fit different eras and body styles (slipperier cars support a slightly higher constant); very draggy bricks and very slick racers drift outside. Run the math at your own weight honestly measured (full tank, driver aboard) — weight error transfers 1:1 into the power estimate.

For a 3400-lb car with driver: 100 mph ≈ 265 hp, 110 ≈ 350 hp, 120 ≈ 455 hp, 130 ≈ 580 hp — the cube means every 10 mph costs disproportionately more power. It's also why 'just 5 more mph' at the top end is a bigger build than it sounds, and why weight reduction shows up at the traps immediately: 100 lb off a 350-hp car buys about 1 mph.

The 234-cubed correlation was fitted to flywheel (crank) ratings of the muscle-car era, so its output is crank-ish; this tool also shows an ~85% wheel estimate for comparing against chassis-dyno sheets. Mind the variables when reconciling: dyno correction factors (SAE vs STD), drivetrain type (AWD loses more than RWD), and density altitude on race day — a 3000-ft DA day costs roughly 3 mph of trap speed versus sea level.