How to Choose the Right Size Carry-On Bag

You've seen it happen at the gate. Someone rolls up with a bag that looked fine at home, the agent points at the metal sizer by the desk, and the bag doesn't drop in. Now it's a checked bag, a fee, and a wait at the carousel on the other end.

You avoid all of that by sizing the bag properly, and the right size isn't a single number. It's the smallest bag that still carries what you need for the trip while staying inside both limits your airlines enforce: the dimensions, and the weight. Size it right and the bag stays with you the whole way, so you skip the checked bag altogether.

The short version

• Measure your bag to its furthest points, wheels and handles included. Then buy under the tightest figure in each dimension across the airlines you fly. That's your ceiling, whatever your usual carrier prints.
• US domestic carriers cap the dimensions (about 22 x 14 x 9 in / 56 x 36 x 23 cm). Plenty of international and low-cost carriers cap the weight as well, usually around 7 to 10 kg (15 to 22 lb), and they check it.
• Size it to the trip: roughly 20 to 35 liters for one to three nights, 40 to 45 liters for a week.
• Soft-sided bags flex into a tight bin and weigh the least. Hard-shell cases protect what's inside but give you nothing when the bin is full. Wheels add weight and take room from the inside.
• Use your personal item, and buy a bag that sits a little under the limit, so a full pack still fits.

What size is a carry-on bag?

For most US airlines, a carry-on can be up to 22 x 14 x 9 inches (56 x 36 x 23 cm), and that measurement takes in the wheels and the handles. So measure the whole bag, not the part you pack into. That's the figure United, American, Delta and the other big domestic carriers print, and it's where to start if you fly mostly inside the US.

There's no worldwide standard, though. Plenty of airlines outside the US work to a different cabin limit, often around 55 x 40 x 20 cm (21.7 x 15.7 x 7.9 in), close to what the IATA airline trade body suggests. That limit is 1 cm shorter than the US figure and 3 cm shallower, but 4 cm wider, so neither one is simply smaller than the other. A bag built to the US maximum is over on two of the three dimensions. Low-cost carriers go smaller still, and some give you only a free bag that fits under the seat, then charge for anything larger in the overhead bin.

Linear inches trips people up first. It's just the three dimensions added together, a single number some airlines quote instead of length by width by depth. The bigger catch is the gap between a bag's outside size and the space inside it. Measure a soft bag across its widest packed bulge and it comes out bigger than the neat rectangle on the label, and the outside is what the agent measures. Read every limit as the outside of a full bag, wheels and handles and all.

Does carry-on weight matter as much as size?

Carry-on weight can matter as much as the dimensions, and on some routes it matters more. On most US domestic flights nobody weighs your carry-on, so the size is the only real limit. Step onto an international route or a low-cost carrier and weight becomes a hard limit of its own, usually somewhere around 7 to 10 kg (15 to 22 lb). Staff at the gate do put bags on the scale.

That mostly means international full-service airlines, Middle-East and Asian carriers and European low-cost airlines. Emirates holds economy cabin bags to 7 kg (15 lb). Lufthansa allows 8 kg (18 lb). The two limits are separate, and your bag has to come in under both. It can sit comfortably inside the size limit and still come off the scale too heavy.

The empty bag comes out of your allowance

Your allowance covers the bag plus everything in it, so the bag's own weight comes out of the total before you pack a single shirt. A rigid case with wheels and a metal handle can weigh 3 to 5 kg (6.5 to 11 lb) before anything goes in. On a 7 kg (15 lb) carrier that leaves you 2 to 4 kg for everything you're actually taking. So weigh the empty bag before you judge it by how much it holds.

A bigger bag can backfire here. Buy the roomiest carry-on you can find for a weight-capped airline and you can end up gate-checking the very bag you bought so this wouldn't happen: you reach the front of the line, the bag goes on the scale, and it comes off again headed for the hold. So if you fly weight-limited routes even sometimes, check the empty weight first, ahead of how roomy the bag looks.

What size carry-on do you need?

The carry-on you need is the smallest one that still carries what you take. The largest bag the airline allows is rarely the one you want: you're lifting more bag into the bin than you needed to, and it's harder to slot into a full one. Capacity is measured in liters, and a rough guide covers most people packing normally:

• One to three nights: 20 to 35 liters. A small cabin bag, clothes and a wash bag, nothing checked.
• Four to seven nights: 40 to 45 liters. A full carry-on near the size limit, packed with a little discipline.
• Longer than a week: you're doing laundry partway or you're checking a bag. A single carry-on stops being realistic for most people.

How you pack shifts these numbers. Packing cubes and a light hand stretch a smaller bag further than its liter rating suggests, so treat the ranges as a starting point. If your trips are mostly quick ones, there's more on sizing a bag for one to three nights.

What if you're carrying a suit?

A suit crammed into an ordinary bag arrives creased, because it has to bend to fit. A garment duffel holds the suit on a hanger inside and lets it curve around the bag instead of bending at a hard line, so the suit arrives ready to wear and the main section still packs like a normal overnight bag. You can see our garment carry-ons here.

Hard-shell, soft-sided, or wheeled: which holds more?

Soft-sided bags hold the most. Two bags can measure the same on the outside and still take very different amounts inside, because the shell and the wheel wells take up room the outside measurement never shows. A soft-sided bag gives you the most usable space and the lightest empty weight, and it squashes into a tight bin where a rigid case won't go. A hard-shell case protects what's inside and won't bulge past its size, which can save you at the gate, but it leaves you no flex when the bin is nearly full.

Wheels and a telescoping handle save your shoulder over a long terminal, and they cost you twice: the mechanism adds 1.5 to 2 kg (3 to 4.5 lb), and the wheel wells take room from the inside.

What about a leather bag?

A soft leather holdall like the Weekender carries like a soft-sided bag: it gives at the sides, it slides into a bin, and it still looks right when you walk into a meeting in a way a scuffed nylon case doesn't. The trade is weight. Leather weighs more than technical nylon, so even a soft leather bag spends more of a strict weight allowance.

So on a strict carrier, weigh the empty bag before you rule anything out on material. A soft leather holdall like the Weekender is 2.2 kg (4.9 lb), which leaves 4.8 kg of a 7 kg (15 lb) allowance to pack. A wheeled case is nearer 4 kg (8.8 lb) empty and leaves 3, so on a tight limit it's the wheels that cost you the allowance, not the leather. You can see how the soft leather holdalls are sized here.

How big can your personal item be?

There's no single size for a personal item. A common guide is around 18 x 14 x 8 inches (45 x 35 x 20 cm), but airlines set their own, and they're not all as generous as that guide sounds: United allows 9 x 10 x 17 inches (22 x 25 x 43 cm), which is roughly a quarter less room. So take the figure from your own airline. Anything that fits under the seat counts, and that can be a backpack, a tote or a work bag.

The personal item is the second bag most fares include, and using it properly lets you size the main carry-on down. Put the things you want during the flight in it: a laptop, a book, documents, chargers, whatever you'd reach for in your seat. Then the carry-on only has to hold clothes.

The one catch is basic economy, where some airlines drop the free carry-on and give you only the personal item. On those tickets it's your whole allowance, so buy the largest one that still fits under the seat. If you're not sure how the two allowances differ, we break down carry-on vs personal item separately.

How do you make sure a carry-on will fit?

The gate sizer measures the outside of a full bag at its furthest points: the top of the handle, the back of the wheels, the widest part of a packed side. That's usually bigger than the headline figure on the label.

1. Use the maker's published outside dimensions. Buying online you can't measure a soft bag's packed bulge in advance, so those dimensions are all you have to go on.
2. Hold them against every airline you fly, and buy under the tightest figure in each dimension. There isn't one strictest airline, as the US and IATA limits show: each is tighter than the other somewhere. Do it dimension by dimension and every airline in your year is covered.
3. Leave yourself a margin under each of those figures, so the bag still goes in when you've packed it full or the bin is already tight.
4. Measure it with your own tape when it turns up, and test it packed. Do both inside your return window, so a secretly oversized bag goes back before its first trip.

Don't lean on the label. A tag that says carry-on approved is the maker's opinion (and the maker isn't the one standing at the gate), and every airline sets its own limit, so plenty of bags sold as carry-ons sit above a strict cabin size. A bag sized for your usual domestic carrier can still be too long for an international route, and it only takes one trip on the wrong airline to get caught.

We list exact outside dimensions on every bag in our carry-on range, ready to check against your airlines before you order.