Southwest personal item size: what fits in 18.5 × 8.5 × 13.5 in

Short answer: a Southwest personal item must fit within 18.5 × 8.5 × 13.5 in. The Jelkin 25 is 25 × 17 × 14 cm (about 9.8 × 6.7 × 5.5 in); its longest side is well under Southwest's longest allowed dimension of 18.5 in, and at 14 cm deep it clears any under-seat test, so it qualifies as a free under-seat item.

Southwest publishes the most generous cabin allowance of the big US carriers: a carry-on of 24 × 16 × 10 inches (61 × 40.6 × 25.4 cm) and a personal item of 18.5 × 8.5 × 13.5 inches (47 × 21.6 × 34.3 cm). Both are free on every fare, and Southwest does not publish a carry-on weight limit at all.

The roomiest cabin allowance among the US majors

The difference is two inches of length over the standard 22-inch US carry-on, which is more than it sounds on a 737: it is the difference between a case that fits wheels-first and one that has to be turned. On the personal item, Southwest's 18.5-inch length and 8.5-inch depth are close to the American figure, but the extra half inch is welcome when the bag is full.

The consequence for packing is that you rarely need to pay for anything on a three or four day trip. Two cabin pieces, one of them under the seat, cover most short itineraries without touching the hold.

25 × 17 × 14 cm against 18.5 × 8.5 × 13.5 inches: which side is tightest

The bag in inches is 9.8 × 6.7 × 5.5. Sort both sets and compare: 5.5 in against the 8.5 in depth leaves 3.0 in (7.6 cm) of slack; 6.7 in against the 13.5 in height leaves 6.8 in (17.3 cm); 9.8 in against the 18.5 in length leaves 8.7 in (22.1 cm).

So the tightest side is the depth, with three inches to spare — comfortable, but the bag's 9.8 in length has to run along the 18.5 in axis. Laid lengthwise under the seat in front of you, there is no contact with the seat rail; stood on end it does not fit. The case for 25 cm is built on exactly that balance: small enough for the under-seat space, roomy enough for the day.

The real constraint is overhead space, not the sizer

Southwest has historically boarded by position rather than seat, and the airline has been moving to assigned seating, so the mechanics differ by route and date. Either way the pattern is the same: the earlier your position, the more bin space you get, and by the last third of boarding the bins above many rows are gone. Southwest does not generally weigh or measure cabin bags at the gate, which means the practical limit is whether your case fits in what is left.

This is where a soft padded bag has an advantage over a rigid case: it can be pushed into the gap left by two wheeled bags standing wheels-first. That is worth more than a couple of centimetres on paper.

Two cabin pieces change how you divide the load

With both pieces free, the useful split is flight kit versus destination kit. The overhead piece carries clothes, shoes and anything you can live without for three hours. The under-seat piece carries passport, phone, charger, medication, earbuds, a packable layer and a paperback. Southwest's cabins run cold on some aircraft, and a thin layer is easier to carry than to be without.

That division also survives a delay: everything you need for four hours on the ground is in the bag at your feet, not ten rows away. The packing habits for a small bag go into the ordering that makes this work.

Plane changes and connections without a through-checked bag

Southwest connections usually mean a change of aircraft at a hub such as Denver, Las Vegas, Chicago Midway, Baltimore or Dallas Love. On a through flight you stay on board; on a change of gauge you take everything with you, including the under-seat bag. Keep documents and electronics in the small bag so a rebooking at the gate does not involve unpacking a case in the departure lounge.

The pack-flat check before you board

Put the bag on the floor, press the top lightly and look at the front panel from eye level. If the turn-lock is lifting or the panel is domed, something rigid inside is pressing outward. Take it out, lay it flat against the base and close the bag before you measure. A padded bag will give you a little under load, then hold its shape — which is what you want in the cabin, where it will sit upright between your feet instead of folding over. The Jelkin 25 Cloud Bag in jaune poussin measures 9.8 × 6.7 × 5.5 in and about 600 g empty, so it clears the sizer with room to spare.

If you want to see how the outer 25 × 17 × 14 cm translates to usable space once you subtract padding and lining, the full capacity breakdown runs the numbers, and the centimetre and inch conversion covers airline figures in both units.

Allowances change with route, fare type, season and aircraft. The figures below were checked against the airline’s public baggage pages in October 2026 and are given as a guide only — always confirm on the airline’s own site before you fly, and measure your bag packed rather than empty. CloudFlirty is not affiliated with any airline mentioned here.

Frequently asked questions

Is a 25 × 17 × 14 cm bag within Southwest's personal item size?

Yes. Against 18.5 × 8.5 × 13.5 inches it leaves three inches on the tightest edge.

Does Southwest charge for carry-on bags?

No. The carry-on and the personal item are free on every fare, and there is no published carry-on weight limit.

Will I have space in the overhead bin?

It depends on your boarding position. Late boarding often means the bins near your row are full, which is why the under-seat bag matters.

Can I take two bags through security?

Yes. Two cabin pieces are normal; just be ready to lift both into trays.

What should stay in the under-seat bag on a connection?

Passport, boarding pass, phone, medication and charger. A change of aircraft means you carry everything with you.

Check it against the others: the airline personal item size checker puts this allowance next to 18 other carriers and tells you whether a 25 × 17 × 14 cm bag passes.

Questions people ask

What is Southwest's personal item size?

18.5 × 8.5 × 13.5 in. It must fit under the seat in front of you and is free in addition to your carry-on on qualifying fares.

Does a 25 × 17 × 14 cm (9.8 × 6.7 × 5.5 in) bag fit Southwest?

Yes. The bag's longest side is about 9.8 in, shorter than Southwest's longest allowed dimension, and at 14 cm deep it sits well under any under-seat test, so it drops in with room to spare.

Does the limit include handles and wheels?

Yes. Southwest's personal-item figure is the outside of the bag including handles and wheels.