UV protection and polarization do different jobs. UV protection blocks harmful ultraviolet light and is what protects your eyes; look for 100% UV protection or UV400. Polarization cuts glare reflected off water, roads and snow, which makes sunglasses more comfortable but doesn't add UV protection on its own. Lens darkness is separate again: dark lenses without UV protection can be worse than none.
Sunglasses labels mix up three different things: UV protection, polarization and tint. Here is what each does.
UV protection: the must-have
Ultraviolet light can damage the eyes over time. Look for:
- 100% UV protection, or
- UV400, which blocks wavelengths up to 400 nm (UVA and UVB).
Price doesn’t decide UV protection: affordable sunglasses can block 100% UV, and expensive ones should say so too.
Polarization: the comfort upgrade
Polarized lenses block horizontally reflected glare from water, wet roads, cars and snow.
Great for: driving, fishing, boating, beach days. Watch out for: some phone and car screens can look dark or patchy through polarized lenses, and pilots are often advised against them.
Lens categories (tint darkness)
Many sunglasses use the 0 to 4 categories from the international standard:
| Category | Light let through | Use |
|---|---|---|
| 0 | 80 to 100% | Clear or fashion tint |
| 1 | 43 to 80% | Overcast days |
| 2 | 18 to 43% | Everyday sun |
| 3 | 8 to 18% | Bright sun; the most common |
| 4 | 3 to 8% | Very bright conditions; not for driving |
Lens colors
- Gray: true colors, all-round.
- Brown/amber: boosts contrast, good for driving and changing light.
- Green: balanced color with some contrast.
- Mirrored: reduces brightness further; cosmetic and functional.
Choosing sunglasses
- Everyday: UV400, category 2 or 3, gray or brown.
- Driving: polarized, category 2 or 3, brown or gray (not category 4).
- Water and snow: polarized, category 3, wraparound fit.
- Prescription: many frames are available with prescription sun lenses or clip-ons.
Common questions
Are polarized sunglasses better?
For glare from water, roads and snow, yes. They don't protect against UV by themselves, so make sure they're also labeled 100% UV or UV400.
What does UV400 mean?
The lenses block light with wavelengths up to 400 nanometers, which covers UVA and UVB. It is equivalent to 100% UV protection.
Are darker sunglasses more protective?
No. Darkness reduces brightness, not UV. Dark lenses without UV protection let your pupils widen and admit more UV, so always check the UV label.