Which personal-item size fits the most airlines?
We compared 104 numeric under-seat bag policies
A bag that is no larger on any edge cannot fit fewer published boxes. In our test, 35 × 25 × 15 cm and the roomier 40 × 25 × 15 cm tied: both matched 81 of 104 airlines (77.9%) with a numeric personal-item limit. The 40 cm version is the better capacity trade-off among those joint leaders. A roomier 40 × 30 × 15 cm keeps 18 litres of rectangular volume and still matches 77 of 104.
That is a dimensional comparison, not a universal promise. 47 of the 151 airlines in our wider dataset do not have a separate numeric personal-item box in the record, so we exclude them rather than guessing. Fare, combined weight, route, aircraft and operating-carrier rules can also change the answer.
15 L and the same reach as the smaller 35 × 25 × 15 cm sample.
A slim 18 L format with 27 dimensional exceptions in the covered dataset.
Moving from 40 × 30 × 15 to 40 × 30 × 20 cm adds 6 L but crosses more airline limits.
Six common personal-item formats, compared
Green means the bag fits a personal-item allowance marked included in our reference record. If a sample matches only a non-included stored allowance, that portion appears in amber. Grey is the share of the 104 airlines with a numeric personal-item box that does not match. Airlines without a numeric personal-item record are not placed in the grey group.
Exact dimensional matches count as accepted but have no safety margin. Bag volumes are simple rectangular-box volumes and will be larger than the usable space in many real bags.
| Outside size | Box volume | Any match | Included | No match |
|---|---|---|---|---|
| 35 × 25 × 15 cm | 13.1 L | 81/104 | 81/104 | 23 |
| 40 × 25 × 15 cm | 15 L | 81/104 | 81/104 | 23 |
| 40 × 30 × 15 cm | 18 L | 77/104 | 77/104 | 27 |
| 40 × 30 × 20 cm | 24 L | 40/104 | 40/104 | 64 |
| 45 × 35 × 20 cm | 31.5 L | 15/104 | 15/104 | 89 |
| 18 × 14 × 8 in | 33 L | 0/104 | 0/104 | 104 |
The hidden trade-off is usually depth
Compare two boxes with the same 40 cm height and 30 cm width. At 15 cm deep, the bag matches 77 airline records. Increase only the depth to 20 cm and the result falls to 40. You gain 6 litres of theoretical volume but lose 37dimensional matches.
This is why labels such as “under-seat”, “personal item” and “fits low-cost airlines” are not measurements. A backpack may look small from the front yet become too deep once the laptop compartment, bottle pocket and front organiser are full. Measure the bag after packing, not while it is empty on a retailer’s shelf.
A useful buying rule
If you regularly change airlines, look for a soft-sided bag whose packed depth stays near 15 cm and whose other edges stay at or below 40 × 30 cm. If your trips usually use one airline, buy for that airline’s exact free allowance instead—the global compromise gives away capacity you may not need to sacrifice.
Compatibility changes by dataset region
The table compares the 40 × 30 × 15 cm balance pick with the roomier 40 × 30 × 20 cm format. Each airline counts once. These are dataset shares, not passenger-weighted market shares, and an airline’s assigned region does not replace a route-specific rule.
| Dataset region | Numeric policies | 40 × 30 × 15 | 40 × 30 × 20 |
|---|---|---|---|
| Europe | 38 | 31/38 | 12/38 |
| United Kingdom | 5 | 4/5 | 2/5 |
| United States | 12 | 11/12 | 10/12 |
| Canada | 5 | 3/5 | 0/5 |
| Latin America | 14 | 12/14 | 11/14 |
| Middle East | 6 | 3/6 | 0/6 |
| Asia-Pacific | 19 | 9/19 | 3/19 |
| Oceania | 1 | 1/1 | 1/1 |
| Africa | 4 | 3/4 | 1/4 |
Why familiar formats are not worldwide standards
The 40 × 30 × 20 cm format is highly visible because several major European low-cost airlines use it. It still matched only 40 of 104 numeric records here. The larger 45 × 35 × 20 cm format matched 15, while the US-market 18 × 14 × 8 inch box matched 0. The imperial format is slightly larger on every edge than 45 × 35 × 20 cm, so treating the two labels as interchangeable can change the result.
Even our slimmer 40 × 25 × 15 cm sample missed 23 numeric records. There is no obligation for airlines to converge on one personal-item box, and some publish only a verbal “small handbag or laptop bag” rule. The safest source is therefore the operating airline’s current baggage page and the entitlement shown on your booking.
Where 40 × 30 × 15 cm still fails
These 27 airline records publish a personal-item box smaller than the balance pick on at least one edge. Use the official link for the exact fare and route; the displayed allowance is the first personal-item record stored for that airline.
| Airline record | Personal-item reference | Last checked | Official source |
|---|---|---|---|
| Aer Lingus | 33 × 25 × 20 cm | View policy ↗ | |
| Air Arabia | 33 × 25 × 20 cm | View policy ↗ | |
| Air Transat | 43 × 31 × 13 cm | View policy ↗ | |
| AirAsia | 40 × 30 × 10 cm | View policy ↗ | |
| Arajet | 40 × 25 × 20 cm | View policy ↗ | |
| Austrian Airlines | 40 × 30 × 10 cm | View policy ↗ | |
| Biman Bangladesh Airlines | 30 × 25 × 14 cm | View policy ↗ | |
| Brussels Airlines | 40 × 30 × 10 cm | View policy ↗ | |
| Bulgaria Air | 40 × 30 × 10 cm | View policy ↗ | |
| Cebu Pacific | 36 × 20 × 20 cm | View policy ↗ | |
| Copa Airlines | 43 × 25 × 22 cm | View policy ↗ | |
| Croatia Airlines | 40 × 30 × 10 cm | View policy ↗ | |
| Cyprus Airways | 35 × 20 × 20 cm | View policy ↗ | |
| Discover Airlines | 40 × 30 × 10 cm | View policy ↗ | |
| EVA Air | 40 × 30 × 10 cm | View policy ↗ | |
| flydubai | 33 × 25 × 20 cm | View policy ↗ | |
| FlySafair | 40 × 20 × 15 cm | View policy ↗ | |
| Hainan Airlines | 30 × 30 × 20 cm | View policy ↗ | |
| HK Express | 40 × 25 × 20 cm | View policy ↗ | |
| LOT Polish Airlines | 40 × 35 × 12 cm | View policy ↗ | |
| SalamAir | 25 × 33 × 20 cm | View policy ↗ | |
| Scoot | 40 × 30 × 10 cm | View policy ↗ | |
| Singapore Airlines | 40 × 30 × 10 cm | View policy ↗ | |
| STARLUX Airlines | 40 × 30 × 10 cm | View policy ↗ | |
| United Airlines | 43 × 25 × 22 cm | View policy ↗ | |
| VietJet Air | 30 × 20 × 10 cm | View policy ↗ | |
| WestJet | 41 × 33 × 14 cm | View policy ↗ |
What this comparison can—and cannot—tell you
It does test
- • All three packed outside dimensions
- • Every numeric personal-item record in the dataset
- • Bag rotation inside a rectangular sizer
- • Whether the stored allowance is marked included
It does not test
- • A policy that provides no numeric personal-item box
- • Your booking’s fare and loyalty benefits
- • Combined cabin-bag and personal-item weight
- • Route, aircraft or operating-carrier exceptions
Test your packed bag
Enter the outside measurements including wheels, handles and full pockets. The checker compares your bag with all stored personal-item and cabin-bag allowances; confirm the final entitlement with the operating carrier before travel.
Check your bag
Enter your bag’s three dimensions to see which airlines it fits.
Methodology and source window
We analysed the 104 airlines in the FitsOnBoard dataset with at least one numeric personal-item allowance. Each airline counts once; results are not weighted by passenger numbers, routes or market share. The wider dataset contains 151 airlines, but we excluded 47 without a separate numeric personal-item record instead of treating missing information as a failure or an unlimited allowance.
For every sample, we compared its three external edges with every stored personal-item allowance. Edges are sorted longest-to-shortest before comparison, so rotating a rectangular bag is allowed. Exact matches count as dimensionally accepted and leave zero margin. Weight, piece-count and combined-entitlement rules are outside the chart.
The underlying policy checks are dated from 9 Jul 2026 to 24 Sept 2026. Official airline pages are the primary sources, but airlines can change rules without notice. Read the full FitsOnBoard methodology and measurement guide.
Personal-item size FAQ
What personal-item size fits the most airlines?+
The 35 × 25 × 15 cm and 40 × 25 × 15 cm samples tied at 81 of 104 airlines with a numeric personal-item allowance. Because 40 × 25 × 15 cm offers 15 litres instead of 13.1 litres without losing a match in this test, it is the more useful of the joint leaders. For a roomier balance, 40 × 30 × 15 cm matched 77 of 104. None of these results overrides the fare, route or operating carrier on your booking.
Is 40 × 30 × 20 cm a universal personal-item size?+
No. It matched 40 of 104 numeric personal-item policies in this comparison. Its 20 cm depth is often the limiting edge, so a 15 cm-deep bag is materially more compatible.
Does a personal item have to fit under the seat?+
Usually yes: airlines commonly describe it as a small bag, handbag, laptop bag or backpack that fits under the seat in front. The published maximum dimensions and the crew’s instructions still control; exit-row and bulkhead seating can change where it must be stowed.
Do wheels, handles and full pockets count?+
Yes. Compare the packed outside dimensions, including wheels, fixed handles, feet and bulging pockets. A soft bag is not automatically accepted if it cannot compress into the airline sizer without force.
Does this study prove the bag is free?+
No. The chart separately identifies matches to allowances marked included in our reference record. Your fare, loyalty status, route and operating carrier can change the entitlement, and a weight or combined-piece rule may still apply.