Surfboard Volume Dial copyright 2012 Mat Arney

Dial it up. Photo: Mat Arney

The Inertia

How are you meant to measure a surfboard?

No, I mean accurately, and in a way that allows you to compare different surfboards to one another in a meaningful fashion?  I can measure a square no problem; at a push I could recall the Pythagoras equations for the circumference and area of a circle.  But surfboards are different beasts:  3-dimensional shapes comprised of varying and complex parabolic curves.  Frankly put, they are a nightmare to measure, and the result is that, whilst many of us might regularly ride a 6’2” x 18½” x 2¼” squash tail, we all ride remarkably different surfboards.  Does that measurement of width apply all of the way from nose to tail and does your board hold that thickness all the way out to the rails, or does your board’s planshape pull to a point at either end with foiled, knifey, rails?  You see what I mean:  three, incredibly basic, dimensional measurements give you very little clue as to the applicable size of a surfboard.

“There are no readily available formulas for calculating the volume of an irregular object, so the easiest method is liquid displacement.” states Nick Blair of Joistik Surfboards in Australia.  “To my knowledge that method has never been used in the industry by your average custom shaper, so I think that the recent phenomenon of volume’s importance to your everyday surfboard consumer is a direct roll-on effect from the use of machines by most shapers these days.”

Before CNC shaping machines, there is no way that any two boards could be identical, and even now it is unlikely that highly refined features such as bottom contours would be perfectly replicated over and over again when being hand finished.  Nuances in factors such as rail profiles and depths of bottom contours can make a surprisingly large difference, not only to how a surfboard performs, but also to how it feels under your feet.  Which is why it stands to reason that more and more of the major players in surfboard design and production should be including a fourth dimension in their measurements to help surfers to make informed purchases:  volume.  The overall size of a board is one of the key measurements that we ought to consider, surely?  I mean, there are others too, but volume is one single measurement that we can all understand and use as a baseline.


The coaches at the Surf Simply coaching resort out in Costa Rica are unashamed geeks. They’ve been busy cutting up old surfboards and doing some sums to try and make this whole idea more accessible and meaningful to board buyers.  They’ve worked out a single measurement whereby perhaps at some point in the future, if the world champ is asked what size board he’s riding then a reply of “five-nine” or “six-two” will not refer to the length of their surfboard in feet and inches but instead to the ratio of their weight in pounds to their board’s volume in liters.  Ru Hill, Surf Simply‘s owner explains:

“The whole idea of referring to boards by length is misleading, even if you mention the width too. The most significant single measurement is obviously the volume. My 5’7″ is 27.9 liters while my 6’0” is actually a smaller board at only 26.3 liters.”

By considering the volume as the primary dimension of the surfboard, surfer’s can go out and purchase a range of different length surfboards, off the rack, knowing with confidence how the volume is going to compare to the boards that they are used to.  Each subsequent surfboard that they then purchase, whether as a replacement or as their ability improves, can be an informed purchase based on either replicating the feeling of a favorite board, or changing a board’s volume to match improvements in their surfing or varying conditions.

“But that’s not the whole story either,” Hill continues. “If I want to ride what Kelly is riding so that I know what he’s feeling under his feet, then I can’t just buy the same boards as him because Kelly (at 160lb/72.5kg) is 5 pounds (2.25kg) heavier then me. What I need to know is the ratio of pounds to liters those guys are riding. Kelly is riding a 5’9″ Semi Pro 12 which is 24.3 liters, meaning than his ratio of pounds to liters is just under 6.6 (just under 3kg/L).  I’m nowhere near that level and I know that boards that work for me are around 5.8 pounds per liter so when I bought my semi pro 12 I chose a 6’0” which is 26.2 liters.”

Hill and his team of coaches estimate that the biggest board that anyone can duckdive is around 3.4ppl (pounds per liter), while the smallest, “toothpick” surfboard that the pros might ride is around 6.7ppl.  For female surfers the range is slightly shorter, going from 4.5ppl (beginners) through to around 5.5ppl for female pros.

1 2

Join The Inertia Family 

Only the best. We promise.