Failproof Formula for Detecting Correct Tempos

Exsqueeze Me! But does anyone out there know of a formula for figuring out exactly what the tempo should be for a given song.  I'm JUST not a math guy, and it gives me vertigo to consider such a task.  However, it does seem logical that if I did something like count the total beats over the course of the total time to play the song; or even just the 1st verse, and maybe 1st chorus, then dividing that by 4 (or whatever time signature) that might give me the right answer.  I'm so sick of depending on utilities that claim they can pinpoint it, and come nowhere near the correct answer.
KC