We all know that one minute of angle is 1.047" per 100 yards. But most don't know why this is. 100 yards is 300 feet. 300 X 12 = 3600 inches. 3600 X pi (because it's a radius around you) = 11,309.73355 11,309.73355 / 180 (degrees in radius) = 62.83185307 inches per degree 62.83185307 / 60 (minutes in a degree) = 1.047197551 inches per MOA So what does it matter? You've got this front sight hanging out there. If you've got a standard AR front sight, it's .072". It's also a given distance from your eyeball, depending on your cheek weld. Lets go with 23.5 inches because that's my distance with an A2 rifle. 23.5 X pi = 73.82742736 73.82742736 / 180 = .410152374 .410152374 / 60 = .006835873 .072 (front sight width) / .006835873 = 10.53267081 So i know my front sight subtends 10.5 MA So: Distance from eye to front sight times pi = radius. Answer from line one (radius) divided by 180 - one angle. answer from line two (angle) divided by 60 minutes = one MOA Front sight width divided by one MOA = front sight width in MOA.