A personal item is the bag that fits under the seat in front of you, and every airline sets its own limit: 17 x 10 x 9 inches on United, 18 x 14 x 8 on American and Spirit, and no published number at all on Delta and Southwest. A carry-on is the bag for the overhead bin, 22 x 14 x 9 inches on most large US airlines and 24 x 16 x 10 on Southwest. Our travel bags page covers how big a weekend bag should be and how our duffels compare with the carry-on limit. This article is about the smaller bag, the one that has to go under the seat, and how to tell which of your bags is which before a gate agent does it for you.
Thanksgiving week is when the difference costs the most. Last year the TSA expected to screen more than 17.8 million people between the Tuesday before Thanksgiving and the Tuesday after, over 3 million of them on the Sunday alone. Full flights fill the overhead bins early, carry-ons get checked at the gate, and on the cheapest fares the personal item is often the only bag you can bring on board for free.
Personal item and carry-on limits, airline by airline
The personal item limit is the one that varies, and the carry-on limit is close to standard. The figures below come from each airline's own baggage page, read on October 28, 2026. Airlines do change them, so look again before you pack; what the table shows is how far apart they are.
| Airline | Personal item, under the seat | Carry-on, overhead bin | Watch for |
|---|---|---|---|
| United | 17 x 10 x 9 in (43 x 25 x 22 cm) | 22 x 14 x 9 in (56 x 35 x 23 cm), handle and wheels included | Basic Economy: personal item only, except to South America and across the Atlantic or Pacific |
| American | 18 x 14 x 8 in (45 x 35 x 20 cm) | 22 x 14 x 9 in (56 x 36 x 23 cm), handles and wheels included | On regional American Eagle flights, a bag bigger than a personal item is checked at the gate, free |
| Delta | No published size; it must fit under the seat | 22 x 14 x 9 in (56 x 35 x 23 cm), handles and wheels included | Delta Connection flights with 50 seats or fewer: personal items only |
| Southwest | No published size; it must fit under the seat | 24 x 16 x 10 in, wheels, handles and attachments included | One carry-on and one personal item, no fare exceptions listed |
| Spirit | 18 x 14 x 8 in, handles and wheels included | 22 x 18 x 10 in (56 x 46 x 25 cm) | Value fare: personal item only, a carry-on is sold separately |
Three things stand out. United's personal item is the smallest of the large carriers, and its 10-inch side is the one that catches most laptop bags and backpacks. Delta and Southwest publish no size at all, so the space under the seat decides, and that space changes with the aircraft, which is why both Delta and American restrict bags on their smallest regional jets. And the cheapest fares lean on the personal item: on a United Basic Economy ticket within the US, it is the only bag that goes on board, and Spirit's lowest fare includes it but no carry-on.
If the trip continues inside Europe, the limits are in centimeters and generally smaller. Lufthansa, SWISS and Air France allow a personal item of 40 x 30 x 15 cm, about 15.7 x 11.8 x 5.9 inches, and the cheapest Lufthansa and SWISS fares within Europe include nothing else. In July 2026 the European Parliament approved new passenger rules that keep a free personal item of that size on flights in the EU from 2027.
Measure the bag the way the sizer will
Measure your bag packed, from its outside edges, with everything that sticks out included. United, American, Delta and Spirit all count handles and wheels in their limits, and a metal sizer frame counts a bulging front pocket the same way. Product pages, ours included, list the outside of the bag, which is the right number here; we explained why it is the wrong number for fitting things inside in what fits in a mini crossbody.
- Pack the bag the way it will travel, laptop and charger included.
- Measure all three sides at the widest point, over pockets and buckles.
- Fold a soft top handle down. A handle that will not fold adds its height.
- Put your three numbers in order from longest to shortest, and do the same with the airline's limit. Airlines write their limits in different orders (United gives its personal item as 9 x 10 x 17), so compare longest with longest, middle with middle and shortest with shortest.
- If any of your numbers is bigger than the matching limit, the bag is a carry-on on that airline, however small it looks.
Step four is the one people skip. A backpack 15 inches tall, 11 wide and 4 deep sounds comfortably inside United's 17 inches, until its 11 inches meets the 10-inch side of the sizer.
Leather keeps its size, full or empty
A structured leather bag measures the same packed or empty, and that cuts both ways. It is why a leather laptop bag protects what is inside and never surprises you with a bulge, and it is also why it will not squeeze into a sizer the way a half-empty nylon backpack does. Full-grain leather does not stretch to take one more sweater either: a zip forced closed over too much takes the strain at its ends and along the stitching. Size the bag for the trip you are packing, not for the hope that it will give a little at the gate.
Our Rollbag is the clearest example. It is a leather cylinder 19.6 inches long, and its ends are stitched leather discs 9.8 inches (25 cm) across. That is 0.8 inch over the 9-inch depth that United, American and Delta publish for a carry-on, and round leather ends do not fold. If your airline measures it, that inch is real; on Southwest, whose limit is 10 inches, it is within the rule. Waxed canvas gives more: Travelbag sits inside the 22 x 14 x 9 limit with room on every side, and its canvas body flexes where leather would not.
Which of our bags go under the seat
Here is how our bags line up against the two most common personal item limits and the standard carry-on limit. The sizes are the outside of the body as listed on each product page; "over" means at least one side is bigger than the matching side of the limit.
| Bag | Outside size | United personal item, 17 x 10 x 9 | American and Spirit personal item, 18 x 14 x 8 | Carry-on, 22 x 14 x 9 |
|---|---|---|---|---|
| Briefbag | 13" x 8.7" x 3.9" (33 x 22 x 10 cm) | Fits | Fits | Fits |
| Hopebag, 13-inch | 13.8" x 9.4" x 4.7" (35 x 24 x 12 cm) | Fits | Fits | Fits |
| Sandbag | 9.8" x 13" x 4.1" (25 x 33 x 10.5 cm) | Fits, 0.2" to spare | Fits | Fits |
| Daybag | 11" x 15" x 3.9" (28 x 38 x 10 cm) | Over by 1" | Fits | Fits |
| Lawbag, 13-inch | 15" x 11" x 3.9" (38 x 28 x 10 cm) | Over by 1" | Fits | Fits |
| Roadbag | 15.7" x 12.6" x 5.9" (40 x 32 x 15 cm) | Over by 2.6" | Fits | Fits |
| Trabag | 18.9" x 13.8" x 4.7" (48 x 35 x 12 cm) | Over | Over by 0.9" | Fits, 0.2" to spare |
| Travelbag | 20.9" x 9.8" x 7.1" (53 x 25 x 18 cm) | Over by 3.9" | Over by 2.9" | Fits |
| Gentilbag | 19.7" x 13.8" x 8.3" (50 x 35 x 21 cm) | Over | Over | Fits, 0.2" to spare |
| Rollbag | 19.6" x 9.8" x 9.8" (50 x 25 x 25 cm) | Over | Over | Over by 0.8" |
The pattern is easy to read. On United, and above all on Basic Economy, the personal item has to stay under 10 inches on its middle side, which in our range means Briefbag, the 13-inch Hopebag or the waxed canvas Sandbag backpack. On American or Spirit, a slim leather backpack such as Daybag or a 13-inch Lawbag goes under the seat with room to spare. Everything bigger is a carry-on, and of our three travel bags only Gentilbag and Travelbag fit the 22 x 14 x 9 limit on paper. How a leather backpack carries a full day is a separate question, which we covered in what leather backpacks are good at.
Pack the personal item for the moment the carry-on is taken away
On a full holiday flight, plan for the carry-on to be checked at the gate. United tells passengers to keep medication, keys and other essentials in the personal item for exactly that reason, and the FAA requires spare lithium batteries and power banks to stay in the cabin: if your carry-on is checked at the gate or planeside, they have to come out of it. So the personal item is not the bag for whatever is left over. It is the bag that has to get you through the trip if the other one goes into the hold.
- Medication for the whole trip, plus a day
- ID, keys and the wallet or card holder
- Power bank, chargers and cables
- Laptop or tablet, if one is coming
- A light layer for a long day in airports
Then size the personal item for that list, not for the carry-on's overflow. A 13-inch laptop, its charger, a power bank, a card holder and keys fit Briefbag or Hopebag; add a sweater and you are in backpack territory. The toiletries can stay in the carry-on: a Doppbag, 8.7" x 4.7" x 3.9" (22 x 12 x 10 cm), lives inside a duffel and is the one bag on this list nobody needs to measure.
Common mistakes
| The move | What actually happens |
|---|---|
| Assuming a personal item is the same size everywhere | United's middle side is 10 inches, American's is 14; the same bag can be both |
| Comparing sizes in the order they are written | Line up longest with longest; United writes its limit as 9 x 10 x 17 |
| Measuring the bag empty | A soft bag grows as you fill it; measure it packed |
| Leaving out the handle and the front pocket | Airlines count handles and wheels, and a sizer frame counts a bulging pocket |
| Packing the power bank in the carry-on | If the carry-on is checked at the gate, spare batteries have to come out and stay in the cabin |
| Expecting a leather bag to squeeze into the sizer | Structured leather keeps its size full or empty and will not give the last half inch |
| Choosing the carry-on first and the personal item from what is left | On a full flight the personal item is the only bag you are sure to keep with you |
Quick checklist
- Look up your airline's personal item and carry-on limits for your fare, on the airline's own page
- Pack the bag, then measure its three sides at the widest point, handle and pockets included
- Sort both sets of numbers from longest to shortest and compare them side by side
- United Basic Economy within the US: personal item only
- Medication, keys, ID, power bank and chargers go in the personal item
- Leather will not squeeze or stretch: leave the margin at home, not at the gate
Frequently Asked Questions
What size is a personal item on a plane?
It depends on the airline. United allows 17 x 10 x 9 inches, American and Spirit 18 x 14 x 8, and Delta and Southwest publish no size, only that it must fit under the seat in front of you. Measure your bag packed, handles and pockets included, and check your own airline's page before you fly.
Is a backpack a personal item or a carry-on?
A backpack is a personal item when it fits the airline's under-seat limit and goes under the seat; the same backpack is your carry-on if it is bigger or goes in the bin. A slim backpack about 11 x 15 x 4 inches fits American's 18 x 14 x 8 limit but is an inch over United's 10-inch side.
Can a weekender bag be a carry-on?
Yes, if it fits the carry-on limit with its handles: 22 x 14 x 9 inches on most large US airlines, 24 x 16 x 10 on Southwest. Measure it packed, because a soft weekender grows as you fill it. Round duffels need a second look: their ends do not fold, so the diameter you buy is the diameter at the sizer.
What should I keep in my personal item in case my carry-on is gate-checked?
Medication, keys, ID, power banks and spare batteries, chargers and anything valuable or fragile. The FAA requires spare lithium batteries and power banks to stay in the cabin, so they have to come out of a carry-on that is checked at the gate. Packing them in the personal item from the start saves the scramble at the door.
Will a leather bag squeeze into the airline sizer?
A structured leather bag will not. It measures the same full or empty, which protects a laptop but leaves no give at the sizer. A soft canvas bag squeezes a little when lightly packed and bulges when full. Leather also does not stretch to take more, so choose the bag for the size of the trip.
Can I bring a carry-on on Basic Economy?
It depends on the airline. On United, Basic Economy allows only a personal item on most routes, apart from flights to South America and across the Atlantic or Pacific. Spirit's lowest fare includes a personal item but sells the carry-on separately. American, Delta and Southwest show no such fare limit on their carry-on pages, but check your own fare anyway.
Holiday travel turns bag size from a question of taste into a question of rules. Look up your airline's two limits for your fare, measure the bag packed, compare the sides in order, and give the personal item the things you cannot afford to lose. Every travel bag with its measurements is on our travel bags page.
