What the convention comes down to
A ski is described by four published figures.
Tip, waist and tail are widths in millimetres at the shovel, underfoot and at the tail — written as three numbers with hyphens. The waist is the one that decides how the ski floats in soft snow and how quickly it goes from edge to edge on hard snow. Narrow underfoot is a piste ski; wide underfoot is a powder ski; the middle is what the trade calls all-mountain.
Radius, in metres, is the arc the ski’s sidecut would carve if it were laid on edge and allowed to bend. A small radius is a short turn; a large one is a long turn.
Length, in centimetres, is the figure every listing leads with and the one that means least on its own — a 170 cm race ski and a 170 cm powder ski are not comparable objects.
Snowboards are described the same way with one addition: the effective edge and the stance range, which decide how a board behaves rather than how long it is.
What it does not promise
It does not describe the flex, the camber profile or the construction, which are at least as decisive and rarely published as numbers.
It does not tell you what length suits you. Makers publish length ranges against rider weight, and this site prints them; nothing in the convention turns a weight into a ski.
It does not stay stable across a model. A single model is built in five lengths, and the three widths and the radius change at each length. A listing that gives one set of figures for the whole range is giving figures for one length and not saying which.
It is not published by anybody. It is a house convention the whole trade follows, and the numbers are printed on the topsheet because a shop needs them, not because a document requires it.
What it is read alongside
The binding brake width convention, which takes the waist figure. The skin sizing convention, which takes the waist and the length together. Neither the binding standards nor the boot standards touch any of these numbers.
Where it turns up on this site
Every ski shelf, the snowboard shelf, the bindings that mount on them and the skins that are cut to them.
This site handles it in one way, consistently. A ski page prints the three widths and the radius as the maker publishes them, for the length being reviewed, and says so where the maker publishes one set for the whole range. Where the waist is missing, the page says it is missing — because that silence is what makes the brake width question unanswerable.
The questions asked most often
What length should I buy?
Makers publish length ranges against weight and sometimes height, and this site prints those. What it does not do is turn them into a recommendation, because the same skier wants a different length on a piste ski and on a touring ski.
Is a bigger radius better?
It is a longer turn. A 13 m ski carves short arcs on a piste and fights a long one; a 19 m ski is stable at speed and reluctant in a narrow trail. Neither is better and the number says which.
Why does the waist matter so much here?
Because it decides two separate things: what the ski floats on, and what brake width a binding needs. It is the only one of the three widths that appears twice in a purchase.
Last reviewed 28 September 2026