How this estimate works
Most 0-60 calculators only divide weight by horsepower. This one runs a small physics simulation. At launch, the car is limited by how much grip the driven tires have. Once it's moving faster, it's limited by power. Aero drag and rolling resistance slow it the whole way, and a 1-2 upshift costs a fraction of a second.
We tuned the model against ten published magazine tests, from a 116 hp NA Miata to a 545 hp GT-R. On average it lands within about 0.4 seconds of the real 0-60 time. Like magazine tests, it uses a one-foot rollout (the timer starts once the car has already rolled a foot).
Trap speed uses the classic Hale formula: mph = 234 × (hp ÷ weight)^⅓. Trap speed mostly reflects power-to-weight, so it's a better sign of real power than ET is.
Why your real time might differ
Gearing first. A car that needs a 2-3 shift before 60 mph loses time; one that reaches 60 in 2nd gains it.
A peaky engine is slower than its peak number suggests, and a torquey turbo engine is often quicker. Launch control, clutch skill, the surface and tire temperature can swing 0-60 by half a second on their own.
Altitude too: a naturally aspirated engine loses about 3% of its power per 1,000 ft. Denver costs a stock NA Miata around 18 hp.
Weight vs power
Rule of thumb: for straight-line speed, cutting your car's lb-per-hp number in pounds is worth about the same as adding 1 hp. On a 2,500 lb, 150 hp car (about 17 lb/hp), dropping 17 lb ≈ adding 1 hp. Try both in the mod box above. On low-power cars, a weight cut is often the cheaper way to get faster, and it helps braking and cornering too. Check the power-to-weight calculator for the full picture.