The cabin bag everyone recommends, and I skip

In a laundromat open onto the street in Taipei, I counted the same bag three times in one hour. Same boxy silhouette, same compression straps on the sides, same way of standing up on its own when you set it on the ground.

Three people who didn’t know each other and had read the same pages.

I’d read them too. For six months, every time I’ve searched anything about cabin luggage, I keep landing on the same figure, delivered in the same tone reserved, normally, for international standards.

Where the number comes from

Forty centimetres, thirty, twenty.

One of these bags’ listings advertises those three dimensions, a capacity of twenty-four litres, and names two airlines outright (product listing, checked on 11 August 2026). The seller is more honest than half the pages recommending it. It states exactly which gauge its product answers to, and nowhere does it claim that gauge applies anywhere else.

This size is one airline’s boarding rule. Nobody voted on it, and another airline could publish three different numbers tomorrow without answering to anyone.

An object sized around one ticket seller’s rule rarely says so in its title. This one does, and that’s also the main reason I’m passing on it.

Twenty-four litres, or the volume of the box

Take the three numbers on the listing and multiply them. Forty by thirty by twenty comes to twenty-four thousand cubic centimetres. Twenty-four litres.

That’s exactly the capacity the listing advertises (product listing, volume checked on 11 August 2026).

What the seller calls capacity is the volume of the rectangular box the bag has to fit inside. A real bag has walls, seams, a zip running along three sides, a padded back and rounded corners, because no fabric makes a perfect right angle. All of that eats into the twenty-four litres. None of the listings I checked publish a usable volume distinct from the outer one.

My own bag is advertised by its maker at forty litres, a figure I’ve never verified and that probably suffers from the same flaw. The gap is still massive. I’m being offered a drop from forty to twenty-four, for money, to earn the right to board on an airline I fly maybe twice a year.

Fitting a gauge and being comfortable to carry are two different jobs

Twenty centimetres of depth against thirty of width gives you an object deeper than it is wide. The load sits far from your back and high up, because that’s the only way to fill a box.

I’m not going to give you a lecture on biomechanics, I don’t have the qualifications. I can talk about the bag I carry, since I actually carry it: it’s noticeably taller than it is deep, it sits flat against the back, and days covering fifteen kilometres on foot taught me that’s the only parameter that really matters.

What I don’t know, I’ll put on the table right away: these four bags might be excellent to carry. I’ve had none of them on my back, none of their listings publish an empty weight, and I’m not going to dress up a geometric guess as a comfort verdict.

The point I’m sticking to is narrower, and it’s verifiable. These bags were designed around a boarding check. Comfort comes after, if it comes at all.

The regulatory bet, and it needs saying

On 21 January 2026, the European Parliament passed a text providing for a free cabin bag within a limit of one hundred combined centimetres and seven kilos. The Council of Ministers is blocking it. As I write this, none of it is in force.

Most of the French-language web tells the opposite story. I’m not naming names, that’s not my job, but if you read somewhere this winter that the law had passed, you read something false.

In parallel, and since August 2025, the airlines belonging to Airlines for Europe have voluntarily committed to a free personal item of at least forty by thirty by fifteen centimetres. A voluntary commitment, not an obligation.

Do the arithmetic with the listing’s numbers. Forty plus thirty plus twenty comes to ninety combined centimetres, under the hundred-centimetre limit the passed text proposes. And twenty centimetres of depth is five more than the fifteen in the voluntary commitment.

So the bag sits in an odd gap: too deep for the floor airlines agreed to of their own accord, smaller than what a still-blocked text would allow. It’s set to a third value, an airline’s, the only one of the three that can change without warning anyone.

One more detail: the bag’s empty weight would eat into that seven-kilo allowance, and none of the four listings checked publish it.

What I do instead

Nothing clever. I keep the forty-litre bag and the tote, I pack less into it than before, and on the two or three trips a year where an airline enforces its own gauge, I either pay the fee or check the bag.

That costs money. A bag in this category costs roughly what several cabin-bag fees add up to, which makes buying one defensible for someone flying the same airline every week. I’m not that person, and if you are, you don’t need me to do the division.

If I had to buy one anyway, my entry-level criterion would be simple: a listing that publishes empty weight and inner dimensions, not just outer ones. Of the four listings I checked, not one does both.

Three of these four reasons are absences. That’s deliberate. I’d rather pass on a good bag over a silent listing than keep a bag where I don’t know the two numbers that actually decide anything.

No M anywhere in this table. I measured none of these bags myself, touched none of them, and a listing’s dimension doesn’t turn into a personal reading just because I copied it down.

These questions stay open because I don’t buy four bags to rule out four, and the full mechanics are in what I don’t test.

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I should tell you something that undercuts everything above. In April, in Bangkok, I had one sitting in a cart, ready to pay. What stopped me wasn’t any of the arguments in this article: it was the delivery address, a guesthouse I was leaving the day after next. The reasoning came afterward, calmly, once the expense had already been avoided by accident. I distrust myself enough to know what that’s worth, and I’m writing it anyway, because half the material convictions I read elsewhere probably have the same origin.