Baby Got Back

A team of British academics has developed a mathematical formula to determine just how perfect your posterior is.

"The perfect female derriere has firmness to the touch and a resilience that prevents undue wobble or bounce, yet looks soft with flawless skin," said Dr. David Holmes, a psychology lecturer at Manchester Metropolitan University, who devised the formula for measuring one's moons.

And the Rosetta Stone of bootyliciousness is: (S+C) x (B+F) / (T-V).

While it may look complicated, getting to the bottom of the formula is easy, Holmes insists.

First, a woman assesses her assets on a scale from 1 to 20 (1 being worst and 20 best) in the following categories:

* S = overall shape (a ripe peach being just about right)

* C = circularity (rounder is better)

* B = bounciness (less wobble is preferred)

* F = firmness (too much push to that cushion loses points)

* T = skin texture (no cellulite, please)

Then calculate this:

* V = the ratio of one's hips to waist. Finally, do the math.

While everyone may aspire to cans of J.Lo or Jessica Simpson proportions, balance is key to achieving the perfect score of approximately 80.

"Slender thighs and hip-to-waist ratio of 0.7 will frame the perfect bum, well, perfectly," Holmes said.

"Kylie [Minogue] would score amazingly well on sphericality and symmetry. Her bottom is perfect in those categories, more so than the likes of . . . Jennifer Lopez, who has a more curvy posterior," he said.

Interestingly, a poll of 2000 people across England found that while women sided with J. Lo's rump as the best, men preferred Minogue's.

But science really settles nothing, says booty expert Sir-Mix-A-Lot.

"They got to be juicy, round, with a little jiggle to it," the "Baby Got Back" rapper told The Post yesterday, laughing hysterically. "The bubbliness does matter."

But there's only one way to measure the most desirable derriere, he said.

"You know it when you see it," he said. "We could debate this all day."