Surfboard Volume Calculator: The Right Liters for Weight and Skill

26.3 liters or 52.5: for a 165 lb (75 kg) surfer, Firewire’s chart doubles the volume of a board from one end of the skill scale to the other [1]. The tool above makes that chart usable at any weight; what is left is to find out what its answer is worth. Let’s do the math.

What the tool calculates

The tool guesses nothing: it reads Firewire’s volume chart, which gives one volume per weight and per skill level, from advanced to beginner [1]. Between two rows it interpolates in a straight line. For 165 lb (75 kg) at the intermediate level, the default values, it lands on a row of the chart: 32.8 liters, or about 0.44 liter per kilogram of body weight. For 154 lb (70 kg) it joins the 150 and 165 lb rows and shows 30.7 liters.

Over the usual range, about 130 to 200 lb (59 to 91 kg), the chart amounts to multiplying your weight in kilograms by a coefficient: about 0.35 for an advanced surfer, 0.37, 0.44, and 0.53 for the in-between levels, 0.70 for a beginner [1].

The coefficient moves at the extremes

Outside that range the coefficient changes. Firewire’s full chart goes down to 80 lb (36 kg) and up to 240 lb (109 kg): an advanced surfer of 80 lb is given 16 liters, or 0.44 liter per kilogram; at 220 lb (100 kg), 36 liters, or 0.36 [1].

Enlarge diagram

The tool has only five rows, from 130 to 200 lb. Below and above them it scales proportionally to weight, which amounts to keeping the coefficient of the outermost row. Its result then drifts away from the full chart:

The gap runs from 1.1 to 2.9 liters in these three examples: below 130 lb and above 200 lb, Firewire’s chart is the reference, and the tool comes out a little low.

Firewire and Lost: two scales that part ways

Firewire’s chart is not the only reference. Lost publishes a guild factorThe ratio of a board’s volume, in liters, to the surfer’s weight, in kilograms; Lost’s calculator credits it to Whitney Guild, in 2013. for each type of surfer, for shortboards only: 0.34 to 0.36 for an advanced, very fit surfer, 0.36 to 0.38 for average to good fitness and skill, 0.38 to 0.42 for the weekend warrior, 0.40 to 0.50 for a novice or in tough conditions [2].

Enlarge diagram

At 165 lb (75 kg) that gives 25.5 to 27 liters at Lost for the advanced surfer, against 26.3 at Firewire: the two agree. Then they drift apart. Firewire’s beginner, 52.5 liters, is 15 liters above the top of Lost’s range for a novice, 37.5 liters [2]. Lost keeps its ratios for shortboards; a beginner on a bulkier board falls outside them.

What the number cannot know

Conditions shift the result. Lost recommends the low end of its range in warm water and good waves, the high end in poor conditions, in a crowd, or in a thick wetsuit [2]. The French Surfing Federation points out that a wetsuit protects against the cold and gives better buoyancy [3].

More volume also makes paddling easier. In a 2017 study, twenty surfers paddled in a swim flume on five boards that differed only in thickness, from 28.4 to 37.4 liters: on the thicker ones, oxygen consumption and heart rate fell, as did pitch and roll [4]. The study measures paddling, not how easily a board turns: it does not say how far to go.

Finally, there is the water. According to NOAA, seawater averages 35 grams of salt per liter, from 33 to 37 depending on the sea, and its density rises with salinity and as the temperature falls [5]. The same board therefore carries a little more in cold, salty water than in warm or fresh water. We do not put a number on this effect: keep the direction, not the value.

From the number to a board

What is left is turning liters into a size. Torq’s spec sheets publish the volume of every size: for 32.8 liters, these are the closest [6] [7].

At 5’8 the PG-R holds 32.2 liters and the Summer Fish 34.4: a 2.2-liter gap at the same length, which no length would let you guess. Compare the liters on the spec sheets, not the feet.

For a beginner, the tool’s result is not the size of a foam learner board. The French Surfing Federation advises starting on a foam learner board [3]; at Torq, the soft-deck longboard is listed at 66 to 95 liters [8], well above the 52.5 liters of our 165 lb example. For those boards, read the volume on the model’s spec sheet.

For shapes and conditions, see our guide on surfboard volume; for cold water, wetsuit thickness by water temperature; for your first session, the beginner’s guide.

The rule fits in one sentence: calculate the volume, pick the board that comes within a few liters of it, then judge it in the water rather than on paper.

Worth watching

Surf Simply’s animated series shows how an online calculator links weight to volume through a ratio, a 176-lb (80 kg) surfer on a 40-liter board being at 50%, then how to place yourself on its level system.

The video is hosted by YouTube (Google): nothing loads until you play it, and Google may then set cookies.

Julien de Jurquet

Vans, RVs, biking and calculators

Julien de Jurquet writes for Outfarer about camper vans, RVs, biking, and calculators. He reads manuals cover to cover and never lets a number slide without its unit, so your choices rest on math, not promises.

All their articles