The Weingarten Ratio is a ratio used to rate girls. It is a step up from the normal 1-10 scale.
You take the girls hottness (1-10) and divide it by her self esteeem (1-10). You want the resulting number to be as large as possible. Using decimals will give a more accurate number.
Thus, 9/2 is a 4.5, whereas 6.5/5.3 is a 1.2.
Named after Weingarten, the theory is that you want a hot girl who either doesn't realize her value, or is dumb enough to spread her legs for you. A hot girl with high self esteem wont put out, so she's not worth it.
Joe: Dude, I totally met this hot 9
Phil: What's her self esteem?
Joe: Like a 7
Phil: Thats only a 1.3 on the Weingarten Ratio. Not worth it.