Personal Item vs Carry-On: What Is the Difference?
Updated September 2026.
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A personal item is the bag that goes under the seat in front of you. A carry-on is the larger bag that goes in the overhead bin. Most US fares let you bring one of each. The sizes are not the same, and on some cheap tickets the overhead bag is the one that costs money.
United’s under-seat box is 17 x 10 x 9 inches. American’s is 18 x 14 x 8. Southwest publishes 24 x 16 x 10 for the overhead bag and no inches at all for the bag under the seat. Frontier includes only the under-seat bag. If you buy one bag to “work on every airline,” those four facts are the ones that fail first.
Every limit below comes from the airline’s own baggage page, checked on 5 September 2026, except Alaska, last pulled on 13 August 2026. Airlines change fares faster than they change boxes. Where a carrier publishes no number, we say so instead of borrowing one from a blog.
Two Cabin Bags, Two Places
The personal item stays at your feet. Typical examples on US carrier pages are a purse, a briefcase, a laptop bag, and a small backpack. It has to slide fully under the seat. If it doesn’t, the gate treats it as a second carry-on, and most tickets do not include a second one.
The carry-on goes in the bin above you. On five of the big US carriers that box is 22 x 14 x 9 inches, wheels and handles included. Southwest and Frontier allow 24 x 16 x 10. A bag bought to the 22 x 14 x 9 standard clears both. A bag bought to Southwest’s larger box does not clear American, Delta, United, Alaska, or JetBlue.
| Personal item | Carry-on | |
|---|---|---|
| Where it goes | Under the seat | Overhead bin |
| Typical US size | 18 x 14 x 8 in when the airline publishes inches | 22 x 14 x 9 in on most majors |
| Approx volume | 25 to 33 litres | About 45 litres, or 63 on Southwest and Frontier |
| On a standard US fare | Included | Included |
| On United Basic Economy (most domestic) | Included | Not included |
| On Frontier | Included, 35 lb cap | Paid add-on, 35 lb cap |
| On Ryanair | 40 x 30 x 20 cm, included | Paid 10 kg bag with Priority |
Coats, umbrellas, duty-free bags, strollers, and assistive devices usually sit outside both counts. A pet carrier does not. Southwest states the carrier uses either the carry-on slot or the personal item slot.
Size Limits by Airline
Read the personal item column as a separate rule, not a shrink-ray version of the carry-on. United’s under-seat bag is the tightest of the US majors. American publishes 18 x 14 x 8, and Frontier uses that same under-seat box. JetBlue is 17 x 13 x 8. Delta, Southwest, and Alaska tell you to fit it under the seat and stop there.
| Airline | Carry-on | Personal item | Overhead bag on the cheapest fare? |
|---|---|---|---|
| American | 22 x 14 x 9 in | 18 x 14 x 8 in | Yes, including Basic Economy |
| Delta | 22 x 14 x 9 in, 45 linear in | Must fit under the seat | Yes, on every fare |
| United | 22 x 14 x 9 in | 17 x 10 x 9 in (United writes 9 x 10 x 17) | No. Basic Economy is personal item only, except South America, transatlantic, and transpacific |
| Southwest | 24 x 16 x 10 in | Must fit under the seat. No published inches | Yes, on every fare |
| Alaska | 22 x 14 x 9 in, 45 linear in | Purse, briefcase, or laptop bag. No published inches | Yes, including Saver |
| JetBlue | 22 x 14 x 9 in | 17 x 13 x 8 in | Yes, including Blue Basic |
| Frontier | 24 x 16 x 10 in, 35 lb | 18 x 14 x 8 in, 35 lb | No. Personal item only |
| Ryanair | 55 x 40 x 20 cm, 10 kg, paid with Priority | 40 x 30 x 20 cm, under the seat | No. The free bag is the small one |
Southwest’s 24 x 16 x 10 box is the largest overhead allowance among US majors. That is the whole point of a dedicated Southwest carry-on size page: a bag that flies there can fail American, Delta, and United at the sizer. Southwest does not publish a personal item in inches. Aggregators invent 18.5 x 13.5 x 8.5 or 16.25 x 13.5 x 8. Southwest’s own list is a purse, briefcase, laptop case, or backpack that goes under the seat.
Spirit Airlines is missing on purpose. Operations stopped on 2 May 2026 and the remaining flights were cancelled. Any Spirit personal item chart you still see describes an airline you cannot book.
When the Fare Drops the Overhead Bag
On American, Delta, Southwest, Alaska, and JetBlue, the cheap ticket still includes both cabin bags. JetBlue states that outright for Blue Basic. American Basic Economy keeps the carry-on too.
United is the trap left among the US majors. For most domestic Basic Economy trips you get one personal item. You cannot bring a carry-on unless the route is South America, transatlantic, or transpacific. Show up at the gate with an overhead bag on a restricted ticket and you pay United’s bag fee plus a Basic Economy gate handling charge. The under-seat bag is then your entire cabin allowance, and United’s 17 x 10 x 9 box is the one that bag has to clear.
Frontier sells the bin separately. Every ticket includes one personal item at 18 x 14 x 8 inches and 35 pounds. The 24 x 16 x 10 carry-on is an add-on or part of a bundle, and Frontier publishes no flat price for it. Frontier is also the only US carrier in the table with a published cabin weight cap, 35 pounds on both bags.
Ryanair works the same way as Frontier, with a smaller free bag. All fares include one 40 x 30 x 20 cm bag under the seat. The 10 kg overhead bag is tied to Priority & 2 Cabin Bags. easyJet’s free bag is larger, 45 x 36 x 20 cm, and still goes under the seat. A bag cut to American’s 18 x 14 x 8 personal item will not fit Ryanair’s gauge.
Delta Connection flights with 50 seats or fewer are a different kind of drop. Delta still sells you a carry-on, then tags it planeside because the regional cabin has almost no bin space. The personal item is what actually rides with you.
How Much Each Bag Holds
The standard US overhead box is about 45 litres. Southwest’s and Frontier’s larger box is about 63 litres. That is the clothes bag: a few days packed hard, or a week if you are disciplined about liquids.
The personal item is smaller than it looks on a product page. United’s 17 x 10 x 9 box is about 25 litres. JetBlue’s 17 x 13 x 8 is about 29. American’s and Frontier’s 18 x 14 x 8 is about 33. Ryanair’s free bag is about 24 litres. Depth is the number that fails first. An empty daypack that measures 8 inches often bulges to 10 or 12 once you put a laptop and a hoodie in it.
If you need one under-seat bag that clears mixed US airlines, size it to United’s 10-inch middle dimension, not to American’s 14-inch width. A bag built to 18 x 14 x 8 is too tall for United. The shopping versions of that envelope live on our personal item backpacks page. That page still copies 18 x 14 x 8 onto carriers that do not use it, so treat United as 17 x 10 x 9 even when a listing claims “fits all airlines.”
Keep medication, chargers, documents, a power bank, and one change of clothes in the under-seat bag. If the bins fill and the carry-on is tagged at the gate, those items stay with you. Spare lithium batteries have to travel in the cabin anyway.
A Backpack Can Be Either Slot
A backpack is not a third category. It is whichever slot it fits. Under 18 x 14 x 8 on American, or under 17 x 10 x 9 on United, and fully under the seat, it is the personal item. At 22 x 14 x 9 it is the carry-on, and you still get a purse or a slim laptop sleeve underneath.
A 28-litre daypack is the usual miss. Empty, it can look close to the under-seat box. Packed, it will not slide under a United or Frontier seat, and the gate will count it as the overhead bag. Then you no longer have a free personal item sitting on top of it. You have one cabin bag, and you may owe for a second.
On a two-bag ticket the clean split is a roller or a travel pack in the bin and a flat backpack at your feet. On United Basic Economy or Frontier, skip the roller. The under-seat bag is the trip.
Garment Bags Take the Carry-On Slot
A garment bag is not a bonus third item. If it goes in the cabin, it uses the carry-on. American is the US major that writes the exception in inches: a soft-sided garment bag up to 51 inches (130 cm) total, length plus width plus height, as that carry-on. It is still one cabin bag, not a garment bag plus a roller.
JetBlue states it has no hanging closets for garment bags. Delta Connection regionals will valet a hanging bag the same way they valet a roller. The full slot question, including United and Delta wording that still conflicts on some pages, is on whether garment bags count as carry-on.
Buying to the Right Box
Buy the overhead bag to 22 x 14 x 9 inches including wheels and handles if you fly more than one US airline. That is the box American, Delta, United, Alaska, and JetBlue share. Southwest’s extra two inches of width and one of depth are real, and they are wasted the moment you connect onto a 22 x 14 x 9 carrier.
Buy the under-seat bag to 17 x 10 x 9 if United or mixed-airline trips are in the mix. Buy to 18 x 14 x 8 only if you fly American and Frontier and you are willing to gate-check or pay on United. Soft sides help on unpublished personal items (Delta, Southwest, Alaska), because the test is “does it go under the seat,” not a sizer frame.
If the overhead bag is the one you are shopping for, start with our best carry-on luggage picks and measure the listed dimensions, not the title. Plenty of listings claim 22 x 14 x 9 in the headline and print 14.6 inches in the spec table.
Which Bag to Pack
Pack both when the fare includes both and the trip is more than a long weekend. Put anything you cannot replace on day one in the personal item. Put clothes and liquids in the carry-on, knowing that bag can still be tagged at the gate on a full flight or a 50-seat regional.
Pack only the personal item on United Basic Economy (most domestic), on Frontier unless you paid for the bin, and on Ryanair unless you paid for Priority. Size that one bag to the tightest carrier on the ticket, which is United at 17 x 10 x 9 in the US and Ryanair at 40 x 30 x 20 cm in Europe.
Pack the larger Southwest-shaped roller only on itineraries that stay on Southwest or Frontier. The 24 x 16 x 10 box is a gift on those two airlines and a sizer failure everywhere else in the table.
FAQ
What is the difference between a personal item and a carry-on?
A personal item goes under the seat. A carry-on goes in the overhead bin. On most US fares you get one of each. The personal item is smaller, usually around 18 x 14 x 8 inches when the airline publishes a number, and United’s version is 17 x 10 x 9. The carry-on is usually 22 x 14 x 9 inches, or 24 x 16 x 10 on Southwest and Frontier.
Can I bring both bags on one ticket?
Yes on American, Delta, Southwest, Alaska, and JetBlue, including those carriers’ cheapest fares. No on United Basic Economy for most domestic routes, where you get the personal item only. No on Frontier and Ryanair unless you pay for the overhead bag. Delta Connection aircraft with 50 seats or fewer will take the carry-on at the jet bridge even when the ticket includes it.
What size is a personal item on most airlines?
There is no single US size. American and Frontier publish 18 x 14 x 8 inches. JetBlue publishes 17 x 13 x 8. United publishes 17 x 10 x 9. Delta, Southwest, and Alaska publish no inches and require the bag to fit under the seat. Ryanair’s free bag is 40 x 30 x 20 cm, which is smaller than the US personal item boxes.
Is a carry-on included on United Basic Economy?
Not on most domestic trips. United allows one personal item on Basic Economy unless you are flying to South America, across the Atlantic, or across the Pacific. The personal item still has to fit 17 x 10 x 9 inches. A bag built to American’s 18 x 14 x 8 box is too big for that fare.
Does a backpack count as a personal item or a carry-on?
Whichever slot it fits. A flat backpack that slides under the seat is the personal item. A 40-litre travel pack that only fits the bin is the carry-on. If the packed backpack will not go under the seat, the airline will not let you also bring a rolling carry-on on a one-plus-one ticket.
Do I need a different bag for Southwest than for United?
For the overhead bag, yes if you bought to Southwest’s 24 x 16 x 10 limit. That bag is oversized on United. For the personal item, United is the one that publishes a tight box. A bag that clears 17 x 10 x 9 will go under a Southwest seat. The reverse is not guaranteed, because Southwest never published the number you would check against.
Filed in Travel Tips