How to Choose Sunglasses | Fit, UV Protection & Lens Guide

Picking the right pair comes down to three things: verified UV protection, a fit that stays put without hurting, and coverage that keeps stray light out. Everything else—lens color, polarization, frame style—matters only after those basics are locked in. You don’t need to spend a fortune; here’s the practical sequence.

Check the UV Label First

The most important step is verifying the lenses block ultraviolet light. The American Academy of Ophthalmology (AAO) recommends sunglasses that block 99% to 100% of UVA and UVB rays. Look for one of these labels:

• “100% UV Protection”
• “UV400”
• “100% protection against UVA and UVB”

“UV absorption up to 400nm” means the same as 100% UV absorption. If the label only says “UV protection” without a percentage or UV400 mark, keep shopping. One common trap: dark lenses do not mean better protection. A cheap pair with dark plastic can be worse than no glasses, because your pupils dilate behind them, letting in more unfiltered light. The UV label, not the tint, is the only safety check that matters.

What Fit and Coverage Actually Do

UV protection stops rays that hit the lens, but your eyes also need shielding from light slipping in around the edges. That’s why the AAO says bigger lenses are better—they block more sunlight from the sides—and recommends sunglasses that fit close to your eyes and follow facial contours. REI’s fit checklist covers the physical comfort side: frames should sit snugly on your nose and ears without pinching or rubbing, weight should feel evenly distributed, and your eyelashes shouldn’t brush the frame. If they shift when you look down or shake your head, they’re too loose; if they leave red marks after minutes, they’re too tight.

Frame size is printed on the inside arm as three numbers (e.g., 52-18-140), standing for lens width, bridge width, and temple length in millimeters. The temple length should roughly match the distance from your temple to your ear. Face shape tools are style aids, not safety criteria—use them for aesthetics only.

Lens Quality, Polarization, and Tint

Once the UV label checks out and the frame feels right, focus on the lenses. Choose lenses with exactly matched colors, no visible imperfections, and no distortions. The AAO has a quick in-store test: hold the glasses at a comfortable distance, cover one eye, and look at a rectangular pattern like floor tiles. Move the glasses side to side and up and down. If the lines stay straight, the lenses are fine; if they wiggle, try another pair.

Polarized lenses reduce glare and improve clarity in bright conditions, making them excellent for driving, fishing, or water. But polarization is an added feature, not a substitute for UV protection—you can buy polarized lenses with zero UV blocking, so check the label regardless. For lens darkness, REI’s visible-light transmission (VLT) scale helps match tint to conditions:

Match the tint to your primary use: a dark 10% VLT lens is miserable on a cloudy hike, and a light 60% lens won’t cut it on a beach in July.

Frame the Choice by Activity and Avoid These Mistakes

Frame your final pick around how you’ll use the glasses. Sports call for wraparound styles that stay put and block side glare. Water use demands polarization to cut surface reflection. Prolonged direct sunlight rewards bigger frames and darker tints. Golf and ball sports benefit from tint colors that enhance contrast on grass and sky. If you wear contact lenses, note that only some offer UV protection—and even those don’t cover the whole eye, so sunglasses are still required.

The most common mistakes boil down to a few patterns:

• Buying by style alone and ignoring the UV label.
• Assuming dark lenses equal strong protection.
• Choosing frames that pinch, slip, or sit too small.
• Overlooking side coverage and lens straightness.
• Treating polarized as the same as UV protection.

Once you’ve confirmed UV blocking, nailed the fit, and matched the tint, you’re done—everything else is preference. If you’re ready to look at models that pass these checks, our tested roundup of everyday sunglasses walks through the best options for daily wear.