America Ferrera's long layers flatter her round face shape. Photo: Getty Images

Just like the wrong cut of jean can be unflattering to your derriere, the wrong hair cut can make your face look larger than it really is.

Looking thinner is possible with the right hair cut and style, according to hair stylist Patrick Wellington, founder of Wellington Hair Spa in New York. "We know that square or round faces have a tendency to look fuller and oval shaped faces look thinner, so the key is to work within your facial shape," he tells StyleList.

It's also important to find a stylist who knows how to work with that shape. "If you don't have the right style for your face, it can definitely make you look heavier," Wellington adds. "A good hairstylist should be able to gauge and recommend a suitable look."

Just keep these slimming tricks of the trade in mind:

1. Shoot for a length that falls somewhere between the chin and the shoulder.
2. Steer clear of styles that are too wide.
3. Add some soft fringes or layers around the face to hide part of the cheeks.
4. Use a side part to de-emphasize the round shape of your face.
5. Add some height to the top of your hair to give the illusion of a more oval-shaped silhouette.
6. Avoid blunt-cut bangs.
7. Add contrast with highlights and color -- this will create shading which has a slimming effect.

Wellington also says that brunette to black hair is slimming and short pixie cuts on oval (not round) faces are slimming. "Asymmetrical bobs elongate the neck and make you look slimmer, and long hair with volume and body will also give the allusion of a slimmer face," he adds.

Need more proof? Think about Nikki Blonsky, Jennifer Hudson, Queen Latifah, Raven Symone and America Ferrara. They not only prove that rounder, fuller faces look fabulous with the right hairstyle, they just look downright fabulous, period.

Want to know what else can make you look thinner? Read about these wardrobe tricks!