Personal item size

A personal item is the second, smaller bag airlines let you bring in addition to your main carry-on, meant to fit under the seat in front of you rather than the overhead bin. Purses, small backpacks, laptop bags, and briefcases are the standard examples across nearly every airline's official wording.

It's included free on almost every fare, basic economy included, which makes it the one bag most travelers can count on regardless of how cheap their ticket is. The catch is that "fits under the seat" isn't a fixed measurement, and airlines that do publish a number don't all publish the same one.

No. TSA's own guidance on bag size is unambiguous: "Size dimensions of carry-on baggage allowed in the cabin of the aircraft vary by airline." That covers the personal item as much as the carry-on. TSA screens the contents of your bag, not its dimensions, and it publishes no personal item size rule of its own.

So when a search result promises "the TSA personal item size," what it's actually describing is one airline's policy, dressed up as a universal government rule. There isn't one.

Alaska Airlines, Delta Air Lines, Hawaiian Airlines, Qatar Airways, Southwest Airlines all allow a free personal item, but none of them publish official dimensions for it. Their language is consistently qualitative: it needs to fit under the seat in front of you, without a stated length, width, or height.

If you see a specific personal item size quoted for any of them online, that number is a third-party estimate, not an airline policy. Treat it as a rough guideline at best, and if your bag is borderline, size it to fit comfortably under an average economy seat rather than to a number that isn't actually official.

Emirates is the exception worth knowing before you fly: its standard economy cabins get exactly one cabin piece, with no separate free personal item on top of it. Premium cabins do get a second piece, but the airline documents that as part of a two-piece cabin allowance rather than a personal item in the sense American or United use the term.

If you're used to flying a carrier that always includes a laptop bag on top of your carry-on, this is where that assumption breaks. Anything that doesn't fit in the single cabin allowance has to go in checked baggage.

Because the personal item is free on nearly every fare, a lot of travelers treat it as an afterthought and pack their carry-on carefully while stuffing the personal item with whatever's left over. That's backwards on any airline with a real size check at the gate, since an oversized "personal item" that's actually a second carry-on in disguise is one of the more common reasons people get stopped at boarding.

Notice how much the official range actually spans: from 15.75 x 11.81 x 5.91 inches at the small end to 18 x 14 x 8 inches at the large end. A bag built to the larger figure holds far more, even though both are described the same way, as a free "personal item."

If you want one bag that clears nearly every airline's personal item rule without checking each time, size it to the smallest published figure in the table above, 15.75 x 11.81 x 5.91 inches (Lufthansa, Turkish Airlines). A bag that size also clears every larger allowance, including Allegiant Air's 18 x 14 x 8 inches.

For airlines that don't publish an official number, that same conservative size is still your safest bet, since it's smaller than every stated allowance from every carrier that does publish one. Before a specific trip, run your bag's real measured dimensions through the fit checker to confirm it against your actual airline.