In the market for a new pair of sunglasses? Finding the perfect pair is all about balance. This guide will steer you toward a pair of frames that work perfectly with your face shape.

Know your shape: The most common face shapes are round, oval, rectangle and heart-shaped. Determining your face shape is mainly about your chin and brow. If your chin is defined and pointy, look at how it relates to your hairline and brow to decide if you're a heart or oval. If your chin is squarish, you're more likely to be a rectangle, but if your face is quite long you might be more of an oval. Round faces have smaller chins and fuller cheeks. An Internet search for "common face shapes" will bring up celebrity photo examples, which can be very helpful in determining your own.

Consider scale: If you've got a smaller face, oversized sunglasses may look a bit comic on you. If your face is larger, tiny John Lennon sunnies might appear slightly off.

Create contrast: Wearing a pair of sunglasses that mirrors your face shape will emphasize that shape. Round lenses on a round face will make that face look extremely round, and squarish frames will make a rectangular face look squarish. Choosing a frame that differs from your face's natural shape will create a balanced look.

Note placement: Sunglasses that fit properly should reach the eyebrows at top or they will fail to truly protect your eyes from the sun. Try to avoid styles that jut into your cheeks at the bottom, too.

Sally McGraw is the Minneapolis-based author of Already Pretty (www.alreadypretty.com), a daily blog about the intersection of style and body image.