One centimetre of depth costs you six airlines: a 19-carrier personal item analysis (2026)

Short answer: of the 16 airlines that publish a personal-item size, the tightest depth allowance is 15 cm and the most generous is 25 cm. A bag up to 15 cm deep clears all 16. At 16 cm that falls to 10. At 21 cm it is 3, and past 22 cm only one carrier still takes it.

The cliff sits at 15 cm, not 40

Almost every guide to personal items leads with length. In practice length decides nothing: the shortest published allowance in this analysis is 40 cm, and very few personal items are longer than 35 cm. The number that actually loses you a boarding pass is the third one — depth.

We took the published personal-item allowance for the 19 carriers we track, dropped the three that do not publish a size, and sorted the remaining 16 by depth. The distribution is not gradual. It is a cliff, and the cliff is exactly where a soft bag lands once it is packed.

How the pass rate collapses

Bag depth	Airlines that accept it	Share of the 16	Which ones
up to 15 cm	16	100%	all 16 that publish a size
16–20 cm	10	63%	American, easyJet, Eurowings, Ryanair, Southwest, Spirit, Transavia, United, Vueling, Wizz Air
21 cm	3	19%	Eurowings, Southwest, United
22 cm	2	13%	Eurowings, United
23–25 cm	1	6%	Eurowings

Read the second column and the whole argument is there. Between 15 cm and 16 cm you lose six airlines in one centimetre — Air France, British Airways, Iberia, KLM, Lufthansa and SWISS all cap the under-seat item at 40 × 30 × 15 cm. Nothing else in the category has a step that steep.

Why depth and not length

Published lengths in this set run from 40 cm to 47 cm, and widths from 25.4 cm to 45 cm. A personal item is rarely longer than 35 cm or wider than 25 cm, so on those two axes almost everything passes almost everywhere. Width has one outlier worth knowing: United publishes 25.4 cm, so a 30 cm-wide bag can fail there even if it is shallow.

Depth behaves differently because it is the dimension a bag gains while you pack it. A soft bag that measures 12 cm empty sits at 16–18 cm once it holds a phone, a wallet, keys and a glasses case. That is the gap between "it fits" and "it fits the sizer".

Three carriers publish no size at all

ANA, JAL and Delta do not publish a personal-item dimension. ANA and JAL apply a 115 cm three-edge total to cabin baggage instead; Delta asks only that the item fit under the seat in front of you. For these three, no table — ours included — can tell you the answer. The gate decides, which is a reason to leave more margin, not less.

If your bag is 16–20 cm deep

You are inside 10 of the 16 published allowances, which is fine until your itinerary includes one of the six that cap at 15 cm. Pack the depth last: fill the base and the sides, then decide whether the front pocket is worth it. Note also that Lufthansa's own baggage page lists a gate fee of EUR 60–110 / USD 75–125 for cabin baggage that does not comply, which is well above pre-booked baggage.

If your bag is 21 cm or deeper

Only Eurowings still accepts it, at 25 cm. Southwest drops out at 21.6 cm and United at 22.9 cm, so a bag in that range is effectively a single-airline bag. It can still be a good bag — it just cannot be your travel bag.

What this means for a 25 × 17 × 14 cm bag

14 cm sits one centimetre inside the tightest published depth on the list, and 17 cm of width clears United's 25.4 cm. So the bag passes all 16 without compression, and the margin is thin enough that overpacking can still lose it. That is the honest case for this size: not that it is small, but that its tightest dimension happens to be the one that decides every trip.

Method note

Depth figures are the third number in each carrier's own published personal-item dimensions, taken from the carrier's baggage page and checked on 27 October 2026. Carriers that publish no personal-item size — ANA, JAL, Delta — are excluded from the counts. Figures include handles and wheels where the carrier says so. Limits change; confirm against your booking before flying.

Check a specific bag: the airline personal item size checker runs all 19 carriers side by side. For the length-versus-depth argument end to end, see the 25 cm bag that fits every airline sizer; for the depth caps in detail, Lufthansa and Ryanair bracket the range. The measurement method behind the bag figures is in why external dimensions lie about capacity.