What rifle? I have a 50mm obj on a Savage Bull Barrel in low rings. . . .Gun, mount, barrel all matter. After that, I just do the math from scope center to action = obj + gap I want -barrel taper change from action top to ~ where the obj bell will be.
so,
B = Base height
R = Ring height (base to bottom of scope tube)
T = Scope tube dia
O = Obj outer diameter (scope mfgr's will give this to you or it is on their site or you measure the actual scope
D = Action top - barrel top (to be reasonably accurate, just lay the gun on a sheet of paper and trace it. Then extend the action line(pretty straight) out over the barrel profile. Using pictures or the actual scope figure out where the bell will be closets to the barrel. Then measure the action line to barrel profile distance.) BTW, I just looked at my gun and guessed and was fine. You will be as good as your guess.
G = Barrel to scope gap MIN
** Convert all units to inches.
Then,
B + R + T/2 = O/2 + G + D or solved for R:
R = O/2 +G + D - B - T/2
**If you did this right, this is your minimum ring height.