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What Does UV400 Mean on Sunglasses?

UV400 means the lens blocks all light up to 400 nanometers — 100% of UVA and UVB. It is the one label that matters on any pair of sunglasses.

The short answer: UV400 means the lens blocks all light with wavelengths up to 400 nanometers — which covers 100% of both UVA (315–400 nm) and UVB (280–315 nm) rays. It is the strictest common UV standard for sunglasses, and the one label worth insisting on.

UV400 vs "100% UV protection"

Both labels aim at the same thing, but they are not identical. "100% UV protection" usually references the ANSI standard, which defines UV as ending at 380 nm. UV400 goes 20 nanometers further, closing the small window of high-energy violet-adjacent light that ANSI leaves open. In practice: UV400 ≥ "100% UV" ≥ anything vaguer. Labels like "UV protective" or "blocks UV rays" with no number mean nothing testable.

What UV exposure does to eyes

The damage is cumulative and painless while it happens: cataracts form earlier, macular degeneration risk rises, and the thin skin around the eyes ages faster. Corneal sunburn (photokeratitis) is the acute version — real and painful on snow and water. Sunglasses are the sunscreen your eyes cannot get any other way.

Three facts that surprise people

  • Tint is irrelevant. UV filtering is a property of the lens material and coating. A clear lens can be UV400; a black one can be useless — and then it is worse than nothing.
  • Cheap can be safe. The coating costs cents. The problem with cheap sunglasses is unverified claims, not physics — details here.
  • Clouds do not cancel UV. Up to 80% of UV passes through cloud cover. Overcast beach days burn eyes too.

From our test bench. We photometer-test the UV400 claim on every model before it is listed — a two-minute check most sellers skip. Every frame on Glasses Atlas, from sale pairs to polarized, has passed it.

FAQ

Can UV coating wear off over time?

On quality lenses the UV filter is in the lens material itself, not just a surface layer, so it does not rub off. Deep scratches can compromise cheap surface-coated lenses — one more reason to store frames in a case.

Do prescription glasses have UV protection?

Often, but not automatically. Polycarbonate lenses block UV inherently; standard plastic needs an added coating. Ask your optician what your lenses actually block.

Part of The Complete Guide to Sunglasses Lenses · Last updated: July 19, 2026