01Size the board for the suit, not just the surfer
A tropical board is sized against a body in boardshorts. Here the body wears four or five millimeters of neoprene that soaks up water, stiffens across the shoulders, and quietly steals strokes from every paddle. A 5/4mm suit with boots and hood adds about four and a half kilograms of wet mass and takes real range out of your reach. Size on dry weight alone and the board feels a couple of liters short by the second hour of a winter session.
Fitness matters just as much. A rider who paddles five days a week can live near 0.35 liters per kilogram, while a weekend surfer coming off a desk week does better near 0.46. That gap is eleven hundredths of a liter per kilogram, and on a 75-kilo body it adds up to more than eight liters.
The calculator below folds all of that in. Enter your weight, choose your suit, be honest about your paddle fitness, and pick the wave you chase. It returns a volume in liters, a tail block width, and entry and exit rocker, then reports how much deep-water energy your chosen swell carries, using the rule that wave power scales with height squared times period.
Wetsuit-adjusted volume, rocker & swell-energy calculator
Recommended build
34.1liters
- Tail block width, 12" from tail
- 13 5/8"
- Entry rocker, 12" from nose
- 2 3/16"
- Exit rocker, 12" from tail
- 1"
- Deep-water power, E ∝ H²·T
- 26.3 kW/m
- Against a 4 ft @ 10 s day
- ×3.6
- Energy class
- Solid
Period is inside the 14–18 s window this profile is tuned for.
| Body weight | No suit | 3/2mm | 4/3mm hooded | 5/4mm + boots |
|---|---|---|---|---|
| 60 kg | 24.7 | 26.3 | 27.5 | 29.0 |
| 70 kg | 28.8 | 30.6 | 31.9 | 33.5 |
| 80 kg | 33.0 | 34.8 | 36.2 | 37.9 |
| 90 kg | 37.1 | 39.0 | 40.6 | 42.4 |
02How the numbers become shape
The top drawing is the rocker profile, the side view of the bottom curve, redrawn from your result. Entry rocker is the lift twelve inches back from the nose, and exit rocker is the same measure from the tail. A flatter entry paddles early and trims fast down a long wall, but it pearls in a steep, hollow takeoff. More rocker keeps the nose up and shortens the board in tight pockets.
The lower drawing shows three hull sections cut along the same board. A single concave through the nose gathers water and feeds it toward the planing area. A double concave through the center spreads that flow across both rails and adds speed. A vee through the tail lets the board roll rail to rail without sticking. Rocker and contour are one conversation, which is why we shape them together, and why changing one on the order card usually means we revisit the other.
The energy line deserves a word. Wave power per meter of crest scales as H²·T, so a six-foot swell at sixteen seconds carries about twice the energy of the same height at eight seconds. That is why a long-period groundswell feels heavy at the same buoy height, and why the pointbreak profile asks for a board that holds a line rather than one that pivots.