Online Horsepower Calculators

No its more than just a guesstimate, you just gotta know how to use it properly, and it can be useful, not an absolute though, I've done all manner of cross references with gears/tyre combo's trap rpm's, flyhp numbers ET/mph on my cars and its more or less spot on with what my timeslips were for trap rpm/ET/mph/60's. However, 1 thing has to be a constant....and that is your car has got to be able to Hook reasonably well.....otherwise forget it, the only thing you'll get out of a car that doesn't hook is that is your mph/weight can give you a rough fly hp number for that run.....but it will also show what your ET could've been if you hooked her up and how far your off with your set up.