One thing is for sure, whether you want to believe the Calculator is RWHP or something else, if you are not correcting your track mph for atmospheric conditions before you use the calculator, the number you get will be an actual hp number, which is not what people use when talking chassis and engine dynos numbers. They are always using corrected numbers. And that little piece of cardboard and most on line calculators have no idea if you are in Colorado on a 90°F day or Maryland on a 42°F day.