Is there a reason you want it in clicks rather than just moa or mils? (depending on scope of coarse) it’s a whole lot faster to spin that turret to 4.5 moa rather then count to 18?
Because MOA is just a bit more than an inch. At long ranges they don't match up.
1 MOA = 1.047"
Might not seem much, but a longer ranges it makes a difference in several inches.