How to Read
a Board

A guide · 829 boards to point at

Eight things a board tells you before you read a single number, each shown on boards from the atlas. Every figure here is read off the outline the same way for every board, so two brands can be compared on one footing.

01 · Length and Width

What it says

The first thing a shape tells you is how long it is for how wide. A downwind board can be five times as long as it is wide; a wing board or a surfboard nearer three; a twintip or a wakeboard barely three. Length is waterline: it accelerates onto a bump or a wave and glides once lifted. Width is stability at rest and on touch-downs, and drag once moving. The same three boards, one scale, tails together.

Gong Inflatable I-Prone Trainer 18'0 2026 295 L: 5486 × 533 mm, 10.4 times as long as wide
Slingshot Coalition 2026 157 × 45.9 cm: 1570 × 459 mm, 3.4 times as long as wide
Slingshot Wing Craft V3 90 L: 1499 × 730 mm, 2.0 times as long as wide

02 · The Wide Point

What it says

Where the board is widest, as a share of its length from the tail. Width carried back makes a board plane early and feel loose at the tail; width carried forward keeps a nose that paddles and floats and a tail that holds a line. Stretched to one length and width, these two differ only in where the width sits: 23.5 % and 83.7 % from the tail.

Solid: Slingshot Space Melter 2025, width back. Dashed: Slingshot Glide V14, width forward. Tail at the left.

03 · Tails

The last 40 % of the board, each stretched to one size. A wide, square-ish tail planes early and releases late; a pin holds in and turns on rail; a swallow keeps width for drive with two points that bite. Counts are boards in the atlas with that tail, read off the outline.

04 · Noses

The front 40 %, stretched to one size: how much width the nose keeps. A full nose floats and paddles and forgives a touch-down; a pointed one pierces chop and lets a board run narrow.

05 · Rails

What it says

How quickly the outline pulls in from the wide point. Parallel rails keep their width along the board: more volume for the same length, a straighter line, a board that tracks. Curvy ones narrow early toward both ends: less surface, quicker rail to rail.

Solid: Armstrong Austin Tovey Pro 2025, parallel rails. Dashed: Armstrong Downwind Ocean Mk III, curvy rails.

06 · Rocker

Seen from the side: how much the bottom curves up at the nose and the tail, and how long the flat in between runs. Nose rocker keeps the board from pearling on take-off and softens touch-downs; tail rocker lets it release and turn; the flat is speed. The atlas measures it on the brand’s side photo where there is one, and says so. The Armstrong Downwind Mk III, measured:

Armstrong Downwind Mk III from the side, true proportions: the bottom's rocker over a flat table, every size

Rocker of the 95 L · scaled from the 115 L measured

115 mmtail rocker, at the tip
31 mm12″ from the tail
47 mm12″ from the nose
144 mmnose rocker, at the tip
649 mmflat to within 3 mm, from 31 % to 61 % of the length
44 %of the length to the lowest point, from the tail
162 mmat its thickest, 46 % from the tail
83 mmlonger along the bottom curve than flat

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Rocker of the 105 L · scaled from the 115 L measured

121 mmtail rocker, at the tip
34 mm12″ from the tail
52 mm12″ from the nose
151 mmnose rocker, at the tip
664 mmflat to within 3 mm, from 31 % to 61 % of the length
44 %of the length to the lowest point, from the tail
170 mmat its thickest, 46 % from the tail
87 mmlonger along the bottom curve than flat

Lay this rocker over other boards

Rocker of the 115 L · measured

128 mmtail rocker, at the tip
37 mm12″ from the tail
57 mm12″ from the nose
159 mmnose rocker, at the tip
678 mmflat to within 3 mm, from 32 % to 61 % of the length
44 %of the length to the lowest point, from the tail
170 mmat its thickest, 46 % from the tail · on the photo; Armstrong lists 146 mm
91 mmlonger along the bottom curve than flat

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Rocker of the 125 L · scaled from the 115 L measured

134 mmtail rocker, at the tip
41 mm12″ from the tail
62 mm12″ from the nose
166 mmnose rocker, at the tip
691 mmflat to within 3 mm, from 32 % to 61 % of the length
44 %of the length to the lowest point, from the tail
177 mmat its thickest, 46 % from the tail
95 mmlonger along the bottom curve than flat

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Rocker of the 135 L · scaled from the 115 L measured

139 mmtail rocker, at the tip
43 mm12″ from the tail
66 mm12″ from the nose
172 mmnose rocker, at the tip
701 mmflat to within 3 mm, from 32 % to 61 % of the length
44 %of the length to the lowest point, from the tail
177 mmat its thickest, 46 % from the tail
98 mmlonger along the bottom curve than flat

Lay this rocker over other boards

True proportions · dots at 10 mm and 12″ in from each tip · bracket: flat to within 3 mm · Measured on Armstrong's photo of the 115 L. Tail end set by Claude, not checked by a person.

07 · Thickness and Volume

Volume

Litres are float: the number that sizes most foil and surf boards against your weight. Length × width × thickness is the box a board would fill if it were a brick; a real board fills about 55 to 76 % of it depending on the sport and the build. Inflatables are the fullest, with their boxy rails; kite surfboards the leanest. The atlas calls that share the fullness, and uses it to work out a thickness when a brand lists the litres but not the thickness.

Thickness

Thickness is volume you can’t see from above, and the stiffness of a short board. Brands list it for 2646 of the 3428 sizes in the atlas; for the rest the page says where its figure came from. Twintips and wakeboards list none at all: there the atlas uses a typical figure and labels it as such. Where the numbers come from.

08 · Put It Together

Long and narrow glides and lifts early; short and wide is steady and turns tight; the wide point and the tail decide how it releases; rocker sets how forgiving it is. Now set two boards tails together at one scale and watch the lines disagree.

Compare two boardsFind your size firstor read the typical board of each sport