If you have access to one there is a sight correction chart in Brownells catalog that will help with this. I don't have mine in front of me at the moment. As far as calculating this I have seen the formula - a long time ago so this is from memory and please someone correct me.
50 yds = 1800 inches, 1800 divided by the sight radius of 10.5" is 171.43. Point of impact change will be 171.43 times sight movement. So a movement of .025" x 171.43 equals 4.29" movement at 50 yards. (?) Somebody check me on that.