Researchers at Manchester University commissioned by Bausch & Lomb have discovered the actual formula to beer goggles, as seen on the left. Not as simple as previously thought, the beer goggles effect depends on how much alcohol you've consumed, yes, but also depends on factors like how smoky the room is, how well lit the "person of interest" is, and the distance between the two of you.
It's all quite simple, actually. After you're done calculating, you can see that a person that's not attractive will attractive at Beer Goggle Levels between 51 and 100, and become super-model caliber at BGLs of 100 and up. But good luck doing math when you're hammered.
Beer Goggles effect explained [BBC - Thanks Dave!]