Surfboard volume calculator
Volume in litres is the number that decides whether a board paddles for you. Two boards can both be 5'10" and be twenty per cent apart in float, which is why every listing here states it.
Reading it backwards
Standing in front of a board that says 30 L on the stringer? This is who it fits.
| Ability | Rider weight |
|---|---|
| Beginner | 30 to 33 kg |
| Improver | 40 to 50 kg |
| Intermediate | 55 to 67 kg |
| Advanced | 75 to 86 kg |
| Pro | 86 to 94 kg |
How this is worked out
Body weight multiplied by a litres-per-kilogram factor for your ability, then adjusted for the shape. A beginner sits around 0.90 to 1.00 litres per kilogram, which is roughly their own body weight in litres; an advanced surfer around 0.35 to 0.40. A fish or a twin wants about five per cent more than a shortboard, a step-up about eight, a midlength about a fifth.
It is a starting range, not a prescription. Water temperature, how often you surf and what you are used to all move it, and nobody has ever regretted a litre too many at the end of a three-week trip.
Volume by weight and ability
Litres for a shortboard-style outline. Add roughly five per cent for a fish or a twin, eight for a step-up, a fifth for a midlength, and a quarter for a soft top. Read your own row rather than the one you are working towards: the board that helps you improve is the one you catch waves on.
| Weight | Beginner | Improver | Intermediate | Advanced | Pro |
|---|---|---|---|---|---|
| 50 kg | 45 to 50 | 30 to 37.5 | 22.5 to 27.5 | 17.5 to 20 | 16 to 17.5 |
| 60 kg | 54 to 60 | 36 to 45 | 27 to 33 | 21 to 24 | 19.2 to 21 |
| 70 kg | 63 to 70 | 42 to 52.5 | 31.5 to 38.5 | 24.5 to 28 | 22.4 to 24.5 |
| 75 kg | 67.5 to 75 | 45 to 56.3 | 33.8 to 41.3 | 26.3 to 30 | 24 to 26.3 |
| 80 kg | 72 to 80 | 48 to 60 | 36 to 44 | 28 to 32 | 25.6 to 28 |
| 90 kg | 81 to 90 | 54 to 67.5 | 40.5 to 49.5 | 31.5 to 36 | 28.8 to 31.5 |
| 100 kg | 90 to 100 | 60 to 75 | 45 to 55 | 35 to 40 | 32 to 35 |
A beginner sits near their own body weight in litres. That surprises people who have been shown a shortboard table, which is where most of the bad advice on this subject comes from: those ratios were published for shortboards, and a beginner is not on one.
Where the three measurements are taken
Length runs nose to tail along the stringer, not around the curve. Width is the widest point, which sits behind the middle on almost every board. Thickness is the thickest point, usually just in front of centre. All three are quoted in feet and inches by everyone who sells boards, and in millimetres by everyone who makes them.
You cannot calculate volume from those three numbers. Two boards with identical dimensions differ by several litres depending on how full the rails are, how much the deck domes and how the foam is carried into the nose and tail. A calculator that asks for the three measurements and hands back a volume is estimating, and it will be out by more than the amount you are trying to decide.
This one asks for you instead. Volume printed on a board comes from the shaper's own file and is the only figure worth trusting, which is why every listing here states it and marks it when it was read off a photograph rather than the board.
Why the same litres feel different
Volume tells you how much the board floats. It does not tell you where the float sits, and that is what you feel. Thirty litres spread through a wide, flat fish sits under your chest and pushes you into waves early. The same thirty litres in a narrow step-up is carried under the rails, so it paddles slower and holds a line when the face steepens.
That is why the shape multiplier exists above, and why it is small. Moving from a shortboard to a fish is worth about five per cent, not twenty. If you are switching between board types, change one thing at a time: keep the litres and change the outline, or keep the outline and change the litres.
Two more things move the number and neither is on the form. Cold water means a wetsuit, and a 4/3 adds buoyancy you did not ask for. And how often you surf matters more than how well: someone who paddles four times a week carries less foam comfortably than someone equally skilled who surfs on holiday.
The four ways people get this wrong
Buying the board you want to ride. The most common one by a distance. A board two litres under what you need costs you the waves you would have caught, and you improve by catching waves.
Reading a shortboard table as a beginner table. The ratios most sites publish were written for shortboards. Applied to someone learning, they produce a number for a board that person cannot paddle, let alone stand on.
Trusting a volume nobody measured. A litre figure written on a board in marker is usually right. One calculated from length, width and thickness is a guess. One a seller remembers is a guess about a guess.
Forgetting where you are surfing. Bali in the dry season is not your home beach break. A board that works in soft two-foot waves is a handful at head-high Uluwatu, and a step-up you brought for that is a paddling exercise on a small day at Batu Bolong.