Updated August 2026.
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Southwest Airlines allows one carry-on bag and one personal item per passenger, both for free. No fees. No “basic economy” downgrade that strips your bag allowance. This has been Southwest’s policy for decades and it’s one of the main reasons people fly them despite not having assigned seats or first class.
The carry-on size limit is generous compared to budget carriers, but there are still rules. Here’s exactly what fits, what doesn’t, and what Southwest actually enforces at the gate.
Southwest Carry-On Size Limits
Carry-on bag: 24 x 16 x 10 inches (including handles and wheels). This is larger than many airlines allow. A standard 22-inch carry-on suitcase fits well within these limits. Even some “large carry-on” bags that get flagged on United or American fly fine on Southwest.
Personal item: 18.5 x 13.5 x 8.5 inches. This goes under the seat in front of you. A standard backpack, purse, laptop bag, or briefcase fits. Southwest’s personal item dimensions are slightly larger than some competitors, giving you a bit more room.
Both bags fly free. There’s no weight limit for carry-on bags on Southwest (unlike international carriers that enforce 15-22 pound limits). You can pack your carry-on as heavy as you can lift into the overhead bin.
What Southwest Actually Enforces
Southwest is among the most lenient US carriers for carry-on enforcement. Gate agents rarely pull out measuring devices. If your bag fits in the overhead bin, it’s accepted. The sizer boxes exist at gates but are used mainly when flights are full and bin space is tight.
That said, there are two situations where enforcement happens. On very full flights (holidays, spring break routes), gate agents may check oversized bags and ask passengers to gate-check them for free. And at boarding group C (the last group), overhead space is often gone, meaning your carry-on may need to be gate-checked regardless of size. Getting an earlier boarding position (A or B group) avoids this.
How Southwest Compares to Other Airlines
Southwest’s free bags policy is increasingly rare among US carriers. Here’s how they stack up:
Delta, United, American: One carry-on + one personal item on most fares. Basic economy on some routes restricts you to personal item only. No free checked bags except for elite status.
Spirit and Frontier: Personal item only for free. Carry-on costs $35-$65+ depending on when you pay. This is where Southwest’s policy creates the biggest savings – a round trip with a carry-on on Spirit can cost $70-$130 in bag fees alone.
JetBlue: One carry-on + one personal item on most fares. Similar to mainline carriers. Blue Basic restricts to personal item only.
For travelers who fly with carry-on luggage regularly, Southwest’s free bag policy saves $100-$200 per year compared to Spirit or Frontier, even if the ticket price is slightly higher. The bag fee savings often make Southwest the cheaper total option.
Tips for Flying Southwest with Carry-On
Get Early Bird Check-In or check in exactly 24 hours before departure to secure an A or B boarding group. Boarding position determines your overhead bin access. A1-A30 always gets bin space. B31+ starts getting tight. C group often means gate-checking.
Use a soft-sided bag rather than a hard roller if you’re worried about fit. Soft bags compress and flex into tight bin spaces. Hard cases are all-or-nothing – they fit or they don’t.
Pack a personal item backpack as your “insurance” bag. If your carry-on gets gate-checked, your essentials (laptop, charger, medication, headphones) stay with you under the seat. We covered the best personal item backpacks that maximize under-seat space.
Bags That Fit Southwest’s Limits
Southwest’s numbers are 24 x 16 x 10 for the carry-on and 18.5 x 13.5 x 8.5 for the personal item. These three sit inside those figures and follow the advice above: soft sides for the overhead bin, a real backpack for under the seat.
Travelpro Maxlite 5 Softside Carry-On Luggage Spinner
Twenty three by fourteen and a half by nine leaves margin on every side of Southwest’s limit, and soft sides give you the squeeze the tips above describe when the bin is nearly full. The light empty weight matters here for a different reason than usual: Southwest sets no carry-on weight limit, so the only thing rationing your packing is what you can lift over your head.
Osprey Daylite Expandable 26+6 Travel Pack, Black OS
This is the insurance bag. It clears Southwest’s personal item box on every dimension, so it stays with you under the seat even if the carry-on gets gate-checked in the C group. The two inch expansion is the useful part: zip it closed to go under the seat, open it up once you land.
ECOHUB Travel Backpack 18x14x8 Spirit Airlines...
Built to the 18 x 14 x 8 spec that Spirit and Frontier publish, which is half an inch wider than the figure Southwest lists. In practice it slides under a Southwest seat and no gate agent is measuring a personal item, but the half inch is worth knowing if you are buying one bag to use across every airline.
At a Glance
FAQ
Does Southwest charge for carry-on bags?
No. Southwest allows one carry-on bag and one personal item per passenger for free on all fares. There are no fare classes that restrict your bag allowance. This has been their policy for decades.
What size carry-on does Southwest allow?
24 x 16 x 10 inches, including handles and wheels. This is larger than most US airlines allow. A standard 22-inch carry-on suitcase fits easily within these limits.
Does Southwest have a weight limit for carry-ons?
No. Southwest doesn’t enforce a weight limit for carry-on bags. The only practical limit is what you can lift into the overhead bin yourself. International flights on partner airlines may have different rules.
What happens if my carry-on doesn’t fit on Southwest?
If overhead bin space runs out (common on full flights for late boarding groups), Southwest will gate-check your bag for free. It goes in the cargo hold and you pick it up at the jet bridge or baggage claim upon arrival. Your personal item stays with you under the seat.
Can I bring a backpack and a suitcase on Southwest?
Yes. The suitcase is your carry-on (overhead bin) and the backpack is your personal item (under seat). Both fly free. This is the most common setup for Southwest travelers – a rolling carry-on plus a backpack as a personal item.