There is no single carry-on size — every airline writes its own rules. The short version: most US carriers allow a 56 × 36 × 23 cm carry-on with no weight limit, most European full-service airlines allow 55 × 40 × 23 cm with an 8–12 kg cap, and the big European budget carriers include only a 40 × 30 × 20 cm under-seat bag on a basic fare. The full airline-by-airline chart is below, checked September 2026.
Two bags matter on almost every ticket: the carry-on that goes in the overhead bin, and the smaller personal item that goes under the seat in front of you. Full-service fares usually include both; budget basic fares often include only the personal item. The tables below list both sizes per airline, in centimetres and inches.
US airlines
The good news about American carriers: almost none of them weigh your carry-on on domestic flights — if you can lift it into the bin, you're fine. The catch is Basic Economy on some carriers, and the "personal item only" model on ultra-low-cost airlines.
| Airline | Carry-on (cm) | Carry-on (in) | Personal item (cm) | Weight cap |
|---|---|---|---|---|
| American | 56 × 36 × 23 | 22 × 14 × 9 | 45 × 35 × 20 | None |
| Delta | 56 × 35 × 23 | 22 × 14 × 9 | Fits under seat | None* |
| United | 56 × 35 × 22 | 22 × 14 × 9 | 43 × 25 × 22 | None |
| Southwest | 61 × 41 × 28 | 24 × 16 × 10 | 42 × 33 × 20 | None |
| JetBlue | 56 × 35 × 23 | 22 × 14 × 9 | 43 × 33 × 20 | None |
| Alaska | 56 × 35 × 23 | 22 × 14 × 9 | Fits under seat | None |
| Spirit | 56 × 46 × 25 (paid) | 22 × 18 × 10 | 45 × 35 × 20 free | None |
| Frontier | 61 × 41 × 25 (paid) | 24 × 16 × 10 | 46 × 36 × 20 free | 15.9 kg / 35 lb |
*A few international stations enforce local weight limits on Delta. Southwest is the most generous carry-on in the US; on Spirit and Frontier the free allowance is the personal item only — the bigger bag is a paid add-on.
Canadian airlines
| Airline | Carry-on (cm) | Carry-on (in) | Personal item (cm) | Weight cap |
|---|---|---|---|---|
| Air Canada | 55 × 40 × 23 | 21.5 × 15.5 × 9 | 43 × 33 × 16 | Must lift unaided |
| WestJet | 53 × 38 × 23 | 21 × 15 × 9 | 41 × 33 × 15 | None published |
| Porter | 55 × 40 × 23 | 21.5 × 15.5 × 9 | 43 × 33 × 16 | None published |
| Flair | 55 × 40 × 23 (paid) | 21.5 × 15.5 × 9 | 43 × 33 × 15 free | 7 kg carry-on |
Note WestJet's slightly shorter 53 cm height — a 55 cm case that fits Air Canada can be flagged at a WestJet sizer.
European airlines
Europe is where the gate fees live. The budget carriers include only a small under-seat bag on basic fares — and after the 2025 rule changes, Ryanair and Wizz Air both settled on the same free size: 40 × 30 × 20 cm.
| Airline | Free bag (cm) | Larger cabin bag (cm) | Weight cap |
|---|---|---|---|
| Ryanair | 40 × 30 × 20 under seat | 55 × 40 × 20 with Priority | 10 kg (priority bag) |
| Wizz Air | 40 × 30 × 20 under seat | 55 × 40 × 23 with Priority | 10 kg (priority bag) |
| easyJet | 45 × 36 × 20 under seat | 56 × 45 × 25 (booked) | 15 kg (large bag) |
| Vueling | 40 × 30 × 20 under seat | 55 × 40 × 20 with Priority | 10 kg (priority bag) |
| Lufthansa | 40 × 30 × 10 personal | 55 × 40 × 23 | 8 kg |
| British Airways | 40 × 30 × 15 personal | 56 × 45 × 25 | 23 kg |
| Air France | 40 × 30 × 15 personal | 55 × 35 × 25 | 12 kg combined |
| KLM | 40 × 30 × 15 personal | 55 × 35 × 25 | 12 kg combined |
| Aer Lingus | 48 × 33 × 20 personal | 55 × 40 × 24 | 10 kg |
British Airways is the outlier in a good way — a 23 kg cabin allowance. Air France and KLM count the cabin bag and personal item together toward the weight cap.
The two sizes that solve the whole chart
Look down the tables and a pattern appears. Pack to these two numbers and you're covered almost everywhere:
- 40 × 30 × 20 cm — the strictest free allowance in Europe, and comfortably inside every US personal-item limit. Our full-opening cabin backpacks are built exactly to this size, with the square shape that uses every centimetre the sizer allows.
- 55 × 40 × 20 cm — fits the overhead allowance on the vast majority of full-service carriers and the budget priority bags. The Mirage 360° is built to precisely 55 × 40 × 20; the ultralight Spirit C-Lite 20" keeps you far under Europe's 8–12 kg weight caps at 1.9 kg empty.
Coming home heavier than you left? Pack a flat-folding duffle inside your carry-on on the way out — folded into its own pouch it weighs almost nothing and steals no space. On the return leg, when the shopping and gifts won’t fit the cabin allowance, unfold the Rolling Duffle 120L, fill it, and check it into the hold. One bag out, two bags back.
Five rules that survive every airline
- Pack to the stricter size on multi-airline trips — the tightest sizer on your itinerary decides.
- Measure with the wheels and handles — airlines count them, and the sizer certainly does.
- Mind the weight in Europe — the bag can fit and still fail an 8 kg scale. A light empty bag is half the battle.
- Soft beats rigid at the gate — a soft-sided bag squeezed a centimetre is a bag that fits; a hard shell isn't.
- Check the airline's page the week you fly — allowances changed twice in Europe in the last two years alone.
For the deeper story on why these numbers exist and how to never pay a gate fee, read our cabin size rules guide — and once the bag fits, here's how to get a week inside it.
Sources — check your airline before you fly
Sizes verified September 2026 against the carriers' official baggage pages: American · Delta · United · Southwest · Air Canada · Ryanair · Wizz Air · easyJet · Lufthansa · British Airways. Airlines change allowances without notice — the official page on the day you fly is the only number that counts.
Frequently asked questions
What carry-on size fits all airlines?
No single size fits every airline, but two sizes come close: a 40 × 30 × 20 cm bag fits the free under-seat allowance on Ryanair, Wizz Air and Vueling and counts as a personal item on most North American carriers, and a bag up to 55 × 40 × 20 cm fits the overhead allowance on the great majority of full-service airlines. Always confirm on the airline's own baggage page before flying.
Do US airlines weigh carry-on bags?
Generally no. American, Delta, United, Southwest, JetBlue and Alaska publish size limits for domestic carry-ons but no weight limit — you just need to lift the bag into the bin yourself. European carriers are stricter, with caps of about 8–12 kg on most full-service airlines and 10 kg on budget priority bags.
What is the free cabin bag size on Ryanair and Wizz Air?
On both Ryanair and Wizz Air the bag included with a basic fare must fit 40 × 30 × 20 cm and go under the seat in front of you. A larger bag (up to 55 × 40 × 20 cm on Ryanair, 55 × 40 × 23 cm on Wizz Air, 10 kg) requires a priority or bag add-on.
Is a 40 × 30 × 20 cm backpack big enough for a trip?
For a weekend to about four days, yes — around 20–24 litres packed with compression cubes covers clothes, toiletries and a laptop. Full-opening cabin backpacks built exactly to 40 × 30 × 20 cm make the most of every centimetre the sizer allows.