Pythagoras and the perfect pocket

This post exists because I cracked my phone. I went to put it in the pocket of a pair of shorts, and it turned out the pockets were decorative, they had the shape of a pocket with basically nothing behind it, so the phone glanced off the front of my shorts and met the pavement. And that was that, screen gone, small vendetta born.

So when we built our own shorts, the pockets got the full treatment. Including, at one slightly desperate point, high school maths.

Why are board shorts pockets so useless?

Because pockets are hard to do well on a swim short, and really easy to fake. A real pocket has to hold things without wrecking the line of the shorts, survive being soaked, and not turn into a parachute in the water, and that's a genuine design problem, so a lot of brands just skip it. They stitch on the shape of a pocket with nothing behind it, or they make the opening so small and vertical that a modern phone physically doesn't fit, or the bag is so shallow that everything ejects the moment you sit down.

And the result is the current standard, blokes at the beach carrying their phone in their hand all day like it's 2005 and it's a cigarette.

What makes a pocket actually work?

Geometry, almost entirely. Three numbers have to agree with each other, and most pockets never got introduced to any of them.

The first is the opening width, which decides what physically goes in. It has to clear a phone with a hand still holding it, which is more than the phone's width and way more than most brands allow.

The second is the opening angle, which decides what happens when you move. Too vertical and reaching in is a wrestle, too horizontal and the pocket becomes a chute that empties itself when you sit down, and the right angle lets your hand fall in naturally while keeping everything in when you drop into a chair.

And the third is the bag depth, which decides whether the pocket holds or merely accepts. The phone needs to sit fully below the opening, so it stays put through sitting, jogging across hot sand and the general physics of a big day.

The catch is that those three numbers fight each other. The opening is a diagonal line across the front of the shorts, and its usable width depends on both how far it runs across and how far it drops, so change the angle to keep things from falling out and you've shrunk the effective opening, widen the opening and you've flattened the angle. There's a genuinely small window where everything works at once.

The Pythagoras bit

When we were speccing our pockets, we needed the opening to clear a phone and a hand at a specific angle without pulling the front of the shorts out of shape. Which means the across and down measurements of that diagonal had to be worked backwards from the opening width we wanted, and that is just Pythagoras, a squared plus b squared, dusted off for the first time since year 9 and put to work on shorts.

It ended up in the tech pack as exact figures, our front pocket opening is specced at 17cm and the rear at 15.5, and both get measured on every sample that lands, because pocket dimensions drift in production like everything else does. That's the difference between designing a pocket and drawing one.

Do phones survive in board shorts pockets?

Ours is cut so the phone drops fully below the opening and stays there through a day of sitting, driving and walking, which is the actual job. Water is the caveat we won't fudge, no pocket makes a phone waterproof, so the routine is phone in the pocket for the day, phone out before you're in past your knees.

What the pocket buys you is both hands free for the other twelve hours, and a screen that doesn't meet the pavement outside the fish and chip shop. Keys, cards and a room key live happily in the rear pocket, and the test we built The Collective around is a full day away from the house with nothing in your hands, which, if you've been reading this series, you'll recognise as the same beach to bar test as everything else.

Frequently asked questions

Can you put your phone in board shorts pockets?

In a properly cut pocket, yeah, that's literally what it's for, the opening clears the phone plus your hand and the bag swallows it fully. In most board shorts, no, and it's not you, the pocket was never really designed to hold one.

Why do things fall out of my shorts pockets when I sit down?

The pocket bag is too shallow for the opening angle, so sitting rotates the opening past horizontal and gravity does the rest. It's a geometry fault, not a you fault, and no amount of care fixes a shallow pocket.

Should board shorts pockets have drainage?

Any pocket on a short that's going in the water needs a way for water to get out, or it balloons and drags. It's one of those invisible construction details, like bar tacks, that separates designed shorts from assembled ones, and there's more on those in why most board shorts feel cheaper than they used to.

More in this series: how should board shorts fit and why most board shorts feel cheaper than they used to.