Surfboard volume: what the litres mean and how many you need

Volume is how much space a board takes up, in litres. Nearly all of it is foam, so it is a measure of how much a board floats you: more volume paddles easier and catches waves earlier, less lets you sink a rail and turn harder. Makers print it near the tail, usually on the stringer, beside the length, the width and the thickness.

Length tells you much less. A board can be long and thin or short and thick, and the litres are what decide whether it will paddle for you. That is why volume is the first filter on this site, and why a listing without one is worth less to a buyer than a listing with one.

At 5'10" the board with the most foam in the catalogue floats more than twice what the one with the least does. A groveler like the Sweet Potato is built wide and thick for weak waves; a performance shortboard is pared down to turn. Both are 5'10" in a listing, and only the litres tell them apart.

Volume scales with your body weight and comes down as your ability goes up. These are litres per kilogram of rider. They are not shortboard figures: a beginner's litres describe a soft top or a funboard, because that is the board a beginner should be on.

• Beginner: 0.90 to 1.00 litres per kg
• Improver: 0.60 to 0.75 litres per kg
• Intermediate: 0.45 to 0.55 litres per kg
• Advanced: 0.35 to 0.40 litres per kg
• Pro: 0.32 to 0.35 litres per kg

So a 75 kg intermediate surfer lands around 34 to 41 litres, and a 75 kg beginner near 68 to 75 litres, which is roughly their own bodyweight in litres. That surprises people who have been shown a shortboard table, and it is the number the trade actually uses.

The calculator's surfboard volume chart has the whole ladder, every weight against every level, and works out your own figure from your weight in kilograms or pounds.

Both ends of the shape spectrum want more foam than a performance shortboard, for opposite reasons. A groveler or fish needs float to make weak waves work. A step-up needs paddle speed to get into steep ones. The calculator adds about 5 per cent for a twin fin, 6 per cent for a fish, 8 per cent for a step-up and 18 per cent for a midlength.

Longboards, SUPs and foil boards are not chosen by litres per kilogram at all. Length and outline pick those, and any calculator that gives you a confident litre figure for a longboard is making it up.

The types of surfboards and what each is for are drawn to one scale in their own guide.

• Warm water, no wetsuit: you float slightly less than you do at home in 4 mm of neoprene. Do not size down on arrival.
• Two sessions a day for three weeks: you will be more tired than you plan for. A litre or two extra is not a compromise.
• Reef versus beach break: the same person often wants a smaller board at Uluwatu and a bigger one at Batu Bolong. If you are only buying one board, buy for the wave you will actually surf most.