If you’ve flown Southwest before, you probably know they have a unique way of doing things — open seating, free checked bags, and a generally friendlier vibe than some other big airlines. But while “bags fly free” is a huge plus, you still need to follow the rules when it comes to your carry-on and personal item.
Whether you’re a first-time Southwest flyer or you’ve been flying with them for years, this 2025 guide will walk you through exact carry-on size limits, enforcement practices, special exceptions, and everything else you need to know before you get to the airport.
Quick Reference: Southwest Carry-On Policy 2025
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Carry-on bag allowance: 1
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Personal item allowance: 1
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Carry-on max size: 24 x 16 x 10 inches (handles, wheels, and pockets included)
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Personal item max size: 16.25 x 13.5 x 8 inches
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Weight limit: None (but you must lift it into the overhead bin yourself)
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Fees: $0 for carry-ons and personal items
1. Southwest Carry-On Size Rules
Southwest’s carry-on size allowance is slightly larger than many other U.S. airlines. While airlines like Delta and United have a 22 x 14 x 9 inch limit, Southwest allows 24 x 16 x 10 inches — that’s a bit more space in every dimension.
Why this matters:
If you own a carry-on that barely misses the size limit for other carriers, chances are it will still fit on Southwest. This can save you from having to buy a smaller suitcase just for certain flights.
Important: The size measurement includes the handles, wheels, side pockets, and any protrusions. A bag labeled “22-inch” in stores might measure bigger once you factor in these extras.
How Southwest Measures Carry-Ons
Unlike some budget airlines that force you to place your bag in a sizer frame at check-in, Southwest usually measures visually at the gate. However, if your bag looks oversized, they will ask you to try the sizer.
The sizer dimensions match the 24 x 16 x 10 inch rule. If it fits in the sizer without force, it’s allowed. If not, you’ll need to check it.
2. Southwest Personal Item Rules
Your personal item must fit completely under the seat in front of you. The official limit is 16.25 x 13.5 x 8 inches.
What counts as a personal item:
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Laptop bags
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Small backpacks
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Tote bags
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Slim duffels
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Pet carriers (counts as your personal item)
What doesn’t count:
Larger backpacks, even if they’re “soft,” will often be refused if they don’t fit under the seat — especially on aisle seats where under-seat space is reduced.
Under-Seat Space: Window vs. Middle vs. Aisle
On Southwest’s Boeing 737 fleet, under-seat dimensions vary slightly:
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Window & middle seats: Generally have the most space, enough for a small rolling bag or a large tote.
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Aisle seats: Sometimes have an entertainment box under the seat, which cuts into the space. If you have a bulkier personal item, avoid the aisle if possible.
3. What You Can and Can’t Bring as a Carry-On
Southwest follows TSA guidelines for what’s allowed, but there are also airline-specific restrictions based on size and storage.
Allowed carry-ons (as long as they fit size limits):
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Rolling suitcases
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Travel backpacks
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Garment bags
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Small musical instruments (if they fit in the overhead bin)
Not allowed in the overhead bins:
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Oversized sports equipment (must be checked)
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Items too large to close the bin door
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Loose clothing or coats (must go in the overhead last)
4. Southwest’s Enforcement Policy
Southwest is known for being more relaxed than ultra-low-cost carriers, but don’t mistake that for a free pass. Here’s when you’re most likely to have your bag checked for size:
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During full flights: Overhead bin space runs out faster, and gate agents may be more proactive.
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If your bag visibly bulges: Even softside bags can get flagged if they look overstuffed.
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Late boarding: By the time Group C gets on, most bins are full. Agents may gate-check your bag, even if it’s within size limits.
5. Special Cases and Exceptions
Southwest allows some exceptions for carry-ons that don’t fit the usual category:
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Medical devices: Items like CPAP machines, oxygen concentrators, and mobility aids don’t count toward your carry-on limit.
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Child safety seats: Allowed onboard if you’ve purchased a seat for your child.
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Duty-free purchases: Can be brought onboard in addition to your carry-on and personal item, as long as they fit in storage.
6. Pets as Carry-Ons
Southwest allows small vaccinated domestic cats and dogs in carriers that fit under the seat.
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Pet carrier size limit: 18.5 x 8.5 x 13.5 inches
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Fee: $125 each way
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The pet carrier counts as your personal item, meaning you’ll only be allowed a carry-on in addition.
7. TSA & Security Screening for Carry-Ons
Since Southwest operates entirely within TSA’s jurisdiction for U.S. flights, here’s what you can expect:
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Liquids: Must be in 3.4 oz containers or smaller, inside a quart-size bag.
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Electronics: Laptops and tablets must be removed from your bag unless you have TSA PreCheck.
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Food: Solid food is fine; liquids or gels must follow the 3-1-1 rule.
Southwest doesn’t have its own separate security procedures — everything follows TSA rules. However, larger carry-ons might get extra scrutiny if they’re tightly packed.
8. How Southwest Compares to Other Airlines
| Airline | Carry-On Size Limit (inches) | Personal Item Size (inches) | Weight Limit |
|---|---|---|---|
| Southwest | 24 x 16 x 10 | 16.25 x 13.5 x 8 | None |
| Delta | 22 x 14 x 9 | 18 x 14 x 8 | None |
| United | 22 x 14 x 9 | 17 x 10 x 9 | None |
| American | 22 x 14 x 9 | 18 x 14 x 8 | None |
Southwest offers noticeably more space for carry-ons than most competitors, which is a huge plus for travelers who want to maximize their packing without checking bags.
9. Recommended Carry-On & Personal Item Picks
To make this guide practical for travelers, here are a few bags that fit perfectly within Southwest’s 2025 limits. (Affiliate links open in a new tab.)
Carry-On
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Samsonite Winfield 3 DLX Hardside – 23 x 15 x 9.5 inches, lightweight and durable. [Check price on Amazon]
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Travelpro Maxlite 5 Spinner – 23 x 15.5 x 9 inches, softside flexibility. [Check price on Amazon]
Personal Item
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Samsonite Underseat Carry-On – 16 x 13 x 8 inches, USB port. [Check price on Amazon]
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Travelpro Maxlite 5 Rolling Underseat Bag – 15.5 x 13.5 x 8 inches, smooth wheels. [Check price on Amazon]
10. Final Thoughts
Southwest’s carry-on policy in 2025 is one of the most generous in the U.S., giving passengers more size allowance than competitors and avoiding unnecessary fees. But “generous” doesn’t mean “limitless” — gate agents still enforce the rules when needed.
Key takeaways:
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Measure your bag including wheels and handles.
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Keep personal items compact enough to fit under any seat.
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Arrive early to secure overhead space, especially on full flights.
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Know that medical devices and certain exceptions don’t count toward your limit.
If you stick to these guidelines, you can make the most of Southwest’s relaxed, traveler-friendly approach and avoid the frustration of unexpected gate-checks.
For more detailed carry-on policies from other major airlines, check out my updated guides for American Airlines, Delta Airlines, and United Airlines.