Lenses, not just frames
UV400 Explained: What the Stamp on Sunglasses Actually Means
UV400 means the lens blocks light down to 400 nanometres — UVA and UVB. Darkness is not the feature. A $15 pair can pass. A $300 pair can fail.
Updated 11 Aug 2026 · 7 min read · UV400 explained
400 nanometres is a cutoff, not a vibe
Ultraviolet sits just below the violet you can see. UVB is roughly 280–315nm, UVA 315–400nm. A UV400 lens is specified to block that whole band. “UV400” and “100% UV protection” are meant to be the same shopping claim. “UV400” is more precise; “blocks UV” on a hangtag is not a number.
UVC is already blocked by the atmosphere, so a label bragging about UVC is noise. What you are buying is UVA, which ages the lens of the eye and the skin around it, and UVB, which burns. The frame can be cheap acetate or metal; the lens chemistry is the product.
Dark lenses without UV are worse
Tint reduces visible light. Your pupils open to compensate. If the lens is not filtering UV, you have just built a funnel. That is the whole case against market-stall sunglasses with no stamp, and against costume glasses worn as sunwear on a beach day. A pale UV400 lens is safer than a black unrated one.
This is also why “it feels dark so it must be working” is a bad test. You cannot feel UVA. Polarization, which you can feel as less glare, is a different filter — see polarized versus UV. Indoor blue-light glasses do not cover you outdoors. Different band, different job.
ANSI Z80.3, and the $15 pair that passes
In the US, sunglass lenses are typically tested to ANSI Z80.3. In Europe, ISO 12312-1 and a CE mark with a filter category (0–4). Category 3 is the usual dark sun lens; category 4 is glacier-dark and not for driving. A responsible $15–$30 pharmacy pair can meet UV400 / Z80.3. A $280 fashion pair can be a nylon frame with a tinted window. Ask, or take them to an optician with a UV meter — the test is seconds.
| Label | Means | Does not mean |
|---|---|---|
| UV400 | Cutoff at 400nm, UVA+UVB | Polarized, or expensive |
| 100% UV | Same claim, older wording | A lab you can name |
| ANSI Z80.3 | US sunglass standard | Unbreakable, or stylish |
| CE + cat. 3 | EU filter class, typical sun | UV unless also specified |
| Polarized sticker | Glare filter present | UV400 on its own |
What to buy and what to skip
Everyday: UV400, category 2 or 3, in a shape that covers the eye from the side — wrap or a wide wayfarer that actually shades the orbit. Driving: skip category 4. Kids: the same UV400 standard, not a toy tint. Photochromic clear-to-grey lenses can be UV400; check the fine print, and know they are slower in a cold car.
Skip: no stamp, “UV400” printed only on a removable sticker with no lens marking, and any pair you cannot meter if you are spending real money. Spend on fit and coverage. The filter itself is not a luxury good.
Questions, answered
- Is UV400 better than UV380?
- Slightly, on the long-UVA end. UV400 is the standard to look for. UV380 leaves a slice of UVA. Do not overpay for “UV400+” poetry.
- Can a $15 pair really be UV400?
- Yes. The absorber is cheap. What $15 often skips is hinge quality, honest polarization, and a frame that lasts. Meter them if you are suspicious; do not assume expensive is safer.
- Do I need UV400 on a cloudy day?
- UVA comes through cloud. If you wear the glasses, they should still be UV400. If you take them off, your pupils are at least not dilated behind a tint.
