Waves: a Hawaiian surfer would call this a three-foot wave | Photo: Shutterstock

Why do the Hawaiians measure waves differently from the rest of the world? There are several theories as to why this happens.

Buzzy Trent once said that "waves are not measured in feet and inches, they are measured in increments of fear." While that can be a savvy analysis, it is also true that we need to find ways of comparing different waves.

That is why we measure waves. We do it using the metric system (meter), the imperial system (foot), and the Hawaiian scale.

From an oceanographer's perspective, wave height is measured from the lowest part of the wave (trough) to the highest point of the wave (crest).

During the second half of the 20th century, surf culture developed its own unit of measurement - the body height scale. According to this unique visual unit of measure, you'll get around eight main typical wave sizes:

Ankle-high: one-foot waves;
Knee-high: two-foot waves;
Waist-high: three-foot waves;
Chest-high: four-foot waves;
Shoulder-high: four-to-five-foot waves;
Head-high: five-to-six-foot waves;
Overhead-high: six-to-11-foot waves;
Double overhead-high: 12-foot waves;

Traditionally, worldwide surfers tend to overestimate the size of the waves they ride. Why? Fundamentally because it's human to overestimate our achievements, and our ego is always slightly bigger than the real deal. On the opposite side of the spectrum, you'll find the Hawaiians, known for underestimating wave heights.

The Hawaiian scale is an alternative wave measurement scale expressed in feet that corresponds to roughly 50 percent of the average estimated height of a wave, from trough to crest.

Surfing: the alternative Hawaiian wave scales always underestimates the waves we've ridden | Photo: Shutterstock

As a result, an average surfer who believes he's ridden a 10-foot wave has, from a Hawaiian perspective, surfed a five-to-six-foot roller.

So, why is the gap between the actual wave face observed by 99 percent of the surfing world and the Hawaiian readings so wide?

There are several possible explanations for such a dramatic difference. Some Hawaiians say that it all started in the 1970s when local surfers called waves half as high as they were based on swell heights measured from the offshore buoys and delivered via marine forecasts.

In this case, an eight-foot groundswell at 20 seconds would produce real 15-foot wave faces, but Hawaiians would measure it using the original open ocean swell size, i.e., eight feet.

Others believe there's a reputational side to the Hawaiian wave scale. Islanders like to impress foreign surfers and tourists by undervaluing wave height, thus showing bravery, fearlessness, badassery, and boldness.

There's also another theory that says that Hawaiians believe that a wave should be measured from its back, which almost always results in having smaller measurements in height.

Last but not least, the conspiracy speculation - Hawaiian surfers and lifeguards say their waves are 50 percent smaller than they actually are to make their local surf breaks less attractive to haoles. "It's two-foot out there. Not worth it."

Is the Hawaiian wave height scale more or less scientifically accurate than the most used measurement standard adopted by surf forecasters? We may never know, so it's up to you to decide which one suits you.