Allow me to ramble for a bit, it will be worth it if you shoot open sight rifles much. 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.