Finding the right pair of sunglasses can be a formidable challenge. First, they have to fit properly in order to provide adequate coverage and protection for your eyes. Second, they have to look good and match your personal sense of style. Here's a quick primer on how to find the right fit. (When it comes to style, that's up to you!)
A properly fitting pair of sunglasses will sit more or less flush with your face, with little to no gap underneath your eyes, around the sides, or on top. They should not let light from any angle reach your eyes, including reflected glare from water or snow. But they should not fit so close that they touch your brow or cheeks (do your cheeks push them up when you smile?), or that your eyelashes brush against the inside of the lens (an immediate deal-breaker; your eyelashes will quickly smudge the lenses).
Your sunglasses should also be the proper width for your head. Too wide and you'll notice gaps on the sides where the sunglasses extend away from your face. Too narrow and you'll notice pressure and stretching on the frames across your temples and the side of your head.
If you are buying a pair of sunglasses for active use (running, sports, etc.), they should fit snug enough that they don't shift, slide down your nose, or come flying off when you move your head abruptly. Shake your head vigorously from side-to-side and up-and-down to test this. If you're buying for active use, consider ventilation as well.
One of the drawbacks of a good fit is often reduced airflow (minimal gaps, remember?) which can cause the lenses to fog up if you're getting sweaty. Some styles feature small holes around the frame, especially on top, to address this. Or you can look for a slightly more pronounced gap across the top, which will offer some of the best ventilation (plus it's the easiest gap to address with any brimmed hat).
Common fit challenges? If you have a high bridge on your nose (a.k.a. a big schnoz), it is often difficult to find sunglasses that sit low enough on your face to provide adequate coverage underneath your eyes. Look for sunglasses with a deep and pronounced nose piece, or better yet, an adjustable nose piece that spreads wide enough to fit. Another common fit challenge is a narrow face/head, especially if you're looking for a style with larger lenses—most pairs with large lenses run wide. You may have to settle for smaller lenses for a proper fit.
You can learn more about sunglasses in this past AMC Outdoors article:
Seeing the Light: Protect Your Eyes with the Right Sunglasses
Or this recent post:
A Greener Shade of Sunglasses
“Equipped” is an AMC Outdoors blog, written by Matt Heid.