What this scale settles
It fixes bands of luminous transmittance — the share of visible light a lens passes — and numbers them 0 to 4. The lower the number, the more light gets through.
- Category 0 is nearly clear: night skiing, and the last run in a whiteout.
- Category 1 is a light tint for heavy cloud and falling snow, where contrast matters more than glare.
- Category 2 is the all-round band: usable in cloud, bearable in sun, and what most single-lens goggles ship with.
- Category 3 is for bright sun on snow, and is too dark to read terrain in flat light.
- Category 4 is for extreme glare — glacier, high altitude — and is the one that comes with a road-use restriction in many countries.
The number describes the lens. It says nothing about the frame, the coating, the optical quality or the price.
What it does not promise
It does not describe contrast. Two lenses of the same category can differ enormously in how they render a bump at the edge of a shadow, and the tint colour — rose, amber, grey — is where that happens. No number on the box covers it.
It does not describe glare from wet snow. That is polarisation, a separate property, and a polarised lens can make ice harder to see rather than easier.
It does not promise UV protection. That is a separate declaration, usually printed as UV400, and it is not implied by a dark tint — a cheap dark lens with no UV claim is worse for the eye than a clear one.
It does not cover photochromic behaviour beyond the range declared. How fast a lens darkens, how it behaves in the cold and whether it reaches the top of its range behind a windscreen are all the maker’s claims.
What it is read alongside
The goggle standard covers the object; this scale covers what the lens lets through. Both marks appear on the same product, and a listing that gives one without the other has told you half of what you need.
Where it turns up on this site
Goggles and replacement lenses, and no others — which is unusual on this site, and worth saying: it is the only figure here that describes light.
This site handles it in one way, consistently. Every goggle and lens page prints the category as a category, with the maker named, and prints the photochromic range as a range where one is declared. No page here calls a category 4 better than a category 1, and none of them recommends a category for a day it cannot know.
The questions asked most often
Which category should I buy?
For one lens that has to do everything, category 2 is the all-round answer and the one this shelf sells most of. Two lenses — a 1 and a 3 — cover the season properly, and a photochromic replaces both at a price.
Is category 4 better than category 3?
It is darker. It belongs to glacier light and high-altitude sun, it is dangerous in flat light, and it may not legally be worn driving in some countries — a restriction that belongs to road rules rather than to the lens.
What does a photochromic lens say?
It declares a range rather than a number — S1 to S3, or a wider span again. The claim is the maker’s, and what a lens does at −15 °C is rarely part of it.
Last reviewed 28 September 2026