Check out the 5 different types of butts in the world; which one is yours? (photos)

 There are over 7.4 billion people in the world. All of these people's behinds can be grouped in five categories, according to plastic surgeon Matthew Schulman.

According to Cosmopolitan, over the course of his career, plastic surgeon Matthew Schulman has examined an estimated 50,000 butts from 35 countries. And he's personally augmented more than 2,000 of them.

Dr. Schulman says your butt shape is determined by the placement of your pelvis and hip bones, the 
amount of fat you have and its distribution, the size of your underlying gluteal muscles, and the way your butt muscles attach to the thigh bone. The outcome is a butt that fits into one of five categories.

And in the same way that knowing your breast shape can help you find a flattering bra fit, nailing down your butt shape can determine which underwear styles fit best.

Check out the 5 categories:

1. SQUARE:
If the line between your hip bone and outer thigh runs perpendicular to the ground, congrats, your butt is square, according to Dr. Schulman.

2: V- SHAPE:
If the line between your pelvis and hips angles inward, your butt takes on a "V" shape from behind, according to Dr. Schulman, who says this butt shape is common among women with broad shoulders and very narrow hips.

3. A-SHAPE:
"Pear-shaped" women tend to have A-shaped butts that widen below the hip bones, according to Dr. Schulman.

4. ROUND:

This one is pretty much self-explanatory, but mostly because you've seen this shape on Kim Kardashian, Queen Bey, and J Lo. If you want a rounder butt — which tends to be a popular sentiment among Dr. Schulman's patients — strengthening the butt muscles can give your backside "more projection" without surgical intervention.

5: UPSIDE-DOWN HEART

The ol' upside-down-heart-shaped butt is round without defying gravity. Like round booties, "it involves a curve to the outer hips, but with more volume in the lower part of the hip," Dr. Schulman explains.

Ladies, which one is yours? Guys, which one is your spec?