Why don't shapers include one of the most important pieces of design information on your surfboard? Master craftsman Rusty Preisendorfer enlightens us on the most misunderstood dimension: volume.

What is the volume of your favorite board? You know the length, right? You know the width and even the thickness. Because if you can read the handwriting, it's all right there on the stringer. So why do so few shapers note the volume? It's certainly as important as any other design element. Wouldn't the extra dimension help us choose our boards more wisely? Are we that scared of the metric system?

We at SURFING magazine are ready to embrace the liter. Consider this our official request for "V" to be added to L x H x W on the bottom of our surfboards. Granted, we may be ignorant about the concept right now, but we're ready to learn.

Lucky for us, there are a few brave boardmakers that are ready to pump up the volume. Since the widespread of computer-assisted design (CAD), the number is right there on the screen for us (it previously required a bothersome water displacement tank). Now, Firewire surfboards includes a digital volume calculator on its website. Rusty Surfboards offers a similar volume infographic. Rusty's been analyzing the affects of volume for three decades now, and he happily agreed to educate us a bit on the topic. —Nathan Myers

SURFING: What's the basis of the volume-to-surfer calculation chart?

RUSTY: For most advanced riders, 35% of body weight seems a fairly consistent number for shortboard designs. Advanced riders can feel a variance of a few percentage points, or roughly .5 liters.

That's the metric system, right? I thought we'd already conned the rest of the metric-using world into measuring boards in feet and inches.

Most surfboard-design software calculates volume in metric. Liter is a volume measurement. Kilo is a weight measurement. One liter of water weighs one kilo. One kilogram equals 2.2 pounds. Conversely, one pound equals .4545 kilos.

Can we not do math right now? Math makes me like my surfboard less.

Sure, I was just pointing out the facts. Volume is key, but other elements must be factored in as well, especially area. The balance of volume and area is something shapers keep in mind as they go shorter and longer.

Everyone seems to be going a bit shorter these days. Right?

Shorter, wider "everyday boards" have sparked a lot of interest in volume lately. If you want to go a few inches shorter and a little wider, how do you know if it's enough board for you? Tracking volume helps with the decision.

What's the downside to more volume?

In softer, rolling surf, you will catch more waves, plane through sections and, broadly speaking, stay on top of the water. The drawback is when the surf gets a little better, bigger, punchier, you will find you have a lot less control. You become more of a passenger. Late takeoffs are harder. It's harder to set the rail and fully utilize the rocker.

So what are the advantages of less volume?

The pluses include more control in powerful surf. It's more work to paddle, but easier to penetrate the wave face on takeoffs and turns. Relatively lower volume boards are more sensitive, requiring less effort to engage the rail. But in softer surf, you find the board riding too deep in the water and bogging down.

We still haven't really answered the question: why isn't volume included on the stringer?

Maybe [shapers] just don't want too much info on the board, because it may cause someone to overthink it. We are so used to simply grabbing a rail to check volume, looking at length and width and thickness, and then putting it under our arms. It's such a long-standing ritual. We just feel it.