An easier way to digest it is, measure the group outside to outside to the farthest point, subtract one bullet diameter.
Example: group outside to outside 1" projectile .452 1" - .452" = .548" center to center.
MOA is 1/60 of a degree at a given distance, dangerously close to 1", 1.047197508733" to be exact, at 100 yards, close enough for me, works out to about 10 1/2" at 1,000 yards.