The first problem is that the answer will vary with the particular ammo you use. Variations in bullet weight and muzzle velocity cause this.
If your .22 rimfire is zeroed at fifty yards, you should shoot at a 100-yard target and see how far is the bullet impact below your point of aim. Just guessing, three or four inches or thereabouts. (Been a while since I messed with a .22 at 100 yards.
Say three inches and a 1/4 click scope, that would be 12 clicks.
Never have worried about any formula; always been a "shoot and look" deal for me...