Tit to Gut Ratio
a mathematical approximation of a person's physical attractiveness, most often used as a universal index of comparison among women of varied body types. Other uses include analysis of breast growth on overweight men (see manboob) and, rarely, justification for the use of the phrase BBW.
She would be a 2 if her tit to gut ratio wasn't a 3. That big girl's got enough tits to motorboat for hours.