What Is Good UV Protection for Sunglasses? | The 400nm Standard

For the full breakdown, see our best Women’s UV Protection Sunglasses guide.

The label matters more than the price tag. When you look for sunglasses, the single most important thing to check is that explicit statement: “100% UV protection,” “100% UV-A and UV-B,” or “UV400.” These labels mean the lenses block essentially all ultraviolet radiation up to 400 nm — the full range that reaches your eyes. A $15 pair with the right label protects your eyes just as well as a $300 pair; the science is in the lens treatment, not the brand markup.

What Exactly Does “UV400” Mean?

UV400 is the gold standard for sunglass lenses. It means the lenses block ultraviolet light with wavelengths up to 400 nanometers. That range covers the full spectrum of UV that reaches the Earth’s surface: UVB (280–315 nm), which causes sunburn and corneal damage, and UVA (315–380 nm), which penetrates deeper and contributes to long-term eye damage like cataracts and macular degeneration.

Some labels extend protection to 400 nm, which is why “UV400” is the term you want to see. The European CE labeling system treats 100% UV protection as transmittance below 0.05% up to 380 nm, with “UV 400” extending that guarantee to 400 nm.

What Is the Minimum UV Protection Standard?

It covers UV protection, optical clarity, light transmittance, traffic signal recognition, and physical durability for plano (non-prescription) lenses.

The practical takeaway for shoppers: any pair labeled 100% UV protection or UV400 meets or exceeds these standards. The numbers on the standard itself matter less than the label on the frame. If you see neither label, move on.

Does Darker or More Expensive Mean Better?

No — and this is the most common mistake people make. Lens darkness has nothing to do with UV blocking. A dark lens without UV certification can still let ultraviolet through, and because the tint reduces visible light, your pupils dilate, letting in even more of that unfiltered UV. That’s a worse outcome than wearing no sunglasses at all.

Polarization is also a separate feature. Polarized lenses cut glare from reflective surfaces like water and pavement, but polarization alone proves nothing about UV protection. A pair can be polarized and offer zero UV blocking; conversely, a non-polarized pair can offer complete UV400 protection.

The same logic applies to price. Health Canada explicitly advises that most people can use a low-cost pair if it has proper UVB and UVA protection. There is no authoritative price standard for UV performance — the label is the proof, not the price tag.

Fit and Coverage Matter for Real-World Exposure

UV reaches your eyes from the sides and from above, not just straight ahead. Wraparound or oversized frames reduce side-light exposure, and a brimmed hat adds protection from overhead and scattered UV. For beaches, snow, high altitude, or equatorial settings where reflection increases exposure, broader coverage is especially helpful.

One more note on shopping: a CE mark alone does not guarantee UV400 blocking. CE indicates EU health and safety compliance, but the mark alone doesn’t confirm the 400 nm cutoff. Always look for the explicit 100% UV or UV400 label rather than assuming any certification mark covers it.

If you’re ready to shop now, our tested roundup of the best women’s uv protection sunglasses covers top picks that pass the label check, so you can skip the guesswork.

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