My most obscene drinking occasion was a night of 12 shots of Peppermint Schnapps, followed by a couple beers, and later two matched shots of 151 with a buddy of mine.
I'd say I was drunk then, but I don't really care much for defining my levels of intoxication. I'm much more concerned with what will and won't result in extreme unhappiness both the next day and overall health-wise.
If I had to scale everything though, Bud-light wise I think 4'll get me buzzing, 7'll get me tipsy, and 10'll find me drunk.