Southwest's carry-on size rules
Southwest allows one carry-on bag and one personal item on every flight. Your carry-on bag can be no larger than 24 inches long, 16 inches wide, and 10 inches deep. Your personal item — a purse, backpack, or small bag — must fit under the seat in front of you with no size restriction stated, but it needs to be genuinely small.
Southwest does not use a sizer gate at the airport the way some airlines do, which means bags slightly over the limit sometimes board without issue. That said, if your bag is visibly oversized, gate agents will ask you to check it, and you will pay a checked bag fee. The safest approach is to stay within the stated dimensions.
These limits explore to all Southwest flights, whether you are flying domestically or internationally. The airline counts rolling carry-ons, hard-sided suitcases, soft duffels, and backpacks the same way — by the 24 x 16 x 10 measurement.
Key Takeaways
- Southwest carry-on bags must measure no more than 24 inches long, 16 inches wide, and 10 inches deep, and the airline does not provide a sizer at most gates.
- A personal item like a purse or small backpack travels free in addition to your carry-on and must fit under the seat in front of you.
- Bags that exceed the size limit may be checked at the gate, and you will pay Southwest's checked bag fee if you have already used your two free checked bags.
- Soft-sided luggage compresses slightly, which can help you fit within the limit, while hard-sided suitcases cannot compress and are easier to measure against the stated dimensions.
Carry-on bags that fit Southwest's dimensions
Most 20-inch and 21-inch rolling suitcases fit within Southwest's limit. These are the smallest standard carry-on sizes sold by luggage makers like Samsonite, Away, and Calpak. A 20-inch spinner (four-wheel) suitcase typically measures 20 x 14 x 9 inches, which clears the 24 x 16 x 10 limit with room to spare.
Soft-sided carry-ons compress more easily than hard cases, so a slightly oversized soft bag may still board. Brands like Coolife and IT Luggage make soft-sided 22-inch bags that often pass because the fabric gives when the bag is pushed into the overhead bin. Hard-sided suitcases from brands like Delsey and Rockland are easier to measure but cannot compress, so you need to verify the exact dimensions before buying.
Backpacks and duffels work as carry-ons too. A 40-liter or 45-liter travel backpack usually stays under the limit. Soft duffels are harder to measure because they have no rigid frame, but if it fits comfortably in an overhead bin without bulging, it should pass.
Personal items that travel free with your carry-on
Your personal item is separate from your carry-on and does not count against the size limit. This can be a purse, laptop bag, small backpack, or any bag small enough to slide under the seat in front of you. Many travelers use a crossbody bag or a 10-inch to 12-inch backpack as their personal item.
The personal item is where you keep things you need during the flight — your phone, wallet, medications, a book, or a laptop. It stays with you the entire flight and never goes in the overhead bin. If your personal item is too large to fit under the seat, a gate agent may ask you to check it or combine it with your carry-on.
How to measure your bag before you travel
Use a soft measuring tape or a ruler to check your bag's length, width, and height. Measure the outside of the bag, not the inside. For rolling suitcases, measure from the bottom of the wheels to the top of the handle, the widest point from side to side, and the depth from front to back.
If your bag has wheels, measure the height from the ground to the top of the bag itself, not including the handle. For soft bags, measure when the bag is empty and laid flat. If you are buying a new bag, check the product description on the retailer's website — most luggage listings include the exact dimensions.
Write down the measurements and compare them to Southwest's limit of 24 x 16 x 10. If your bag is 24 x 16 x 10 or smaller in all three dimensions, it will fit. If it exceeds the limit in any direction, it may be checked at the gate.
What happens if your bag is too large
If a gate agent determines your carry-on is oversized, you will be asked to check it. Southwest's first two checked bags fly free for all passengers, so if you have not checked a bag yet, there is no charge. If you have already checked two bags, the third bag costs $35 for the first overage and $50 for each additional bag.
Checking a bag at the gate takes only a few minutes — the agent will tag it and send it to baggage claim. You will retrieve it after you land. This is not ideal if you were counting on having the bag with you during your flight, but it is a straightforward process.
To avoid this situation, measure your bag before you arrive at the airport. If it is borderline, consider packing lighter or using a smaller bag. Soft-sided luggage gives you a small margin because it compresses, but hard cases do not.
Comparing carry-on options for Southwest travel
| Bag Type | Typical Size | Fits Southwest Limit | Best For |
|---|---|---|---|
| 20-inch rolling suitcase | 20 x 14 x 9 inches | Yes | Short trips, overhead bin storage |
| 22-inch soft-sided suitcase | 22 x 15 x 10 inches | Usually, if soft | Slightly more packing space, compresses |
| 24-inch hard-sided suitcase | 24 x 16 x 10 inches | At the limit | Maximum capacity, but no room for error |
| 40-liter travel backpack | Varies, typically 22 x 14 x 10 | Usually | Hands-free travel, flexible shape |
| Personal item (purse, small backpack) | 10 to 14 inches wide | Yes | Essentials during flight, under-seat storage |
Tips for packing within Southwest's carry-on limit
Roll your clothes instead of folding them to save space. Use packing cubes to compress clothing and organize by category. Wear your bulkiest items — jacket, boots, jeans — on the plane instead of packing them. This frees up room in your bag and keeps you warm during the flight.
Pack only what you will actually use. Many travelers overpack out of habit. Before you zip your bag, remove anything you have not touched in the last week. Liquids, gels, and creams take up space; consider buying travel-size versions or waiting to buy them at your destination.
If you are traveling for more than a few days, remember that Southwest includes two free checked bags. You do not have to fit everything into your carry-on. Check a bag if it means you can travel with less stress and more comfort.
Frequently Asked Questions
Can I bring a roller bag and a backpack as my carry-on?
No. You get one carry-on bag and one personal item. The carry-on is your main bag — the roller, backpack, or duffel. The personal item is a smaller bag that goes under the seat. If you bring two full-sized bags, the second one will be checked at the gate.
Do I have to pay for my first checked bag on Southwest?
No. Southwest includes two free checked bags for all passengers on all flights. You pay only if you check a third bag or if you check a bag at the gate because your carry-on was oversized. This is one of Southwest's main advantages over other airlines.
What if my bag is exactly 24 x 16 x 10?
A bag at exactly those dimensions should board without issue. However, if your bag has wheels or a handle that extends beyond those measurements, the total height including the handle may exceed the limit. Measure the bag itself, not the handle.
Can I bring a car seat or stroller as a carry-on?
Car seats and strollers are not counted as carry-on bags. You can bring a car seat and a stroller in addition to your carry-on and personal item. Gate-check them at the jetway if you do not want them in the cabin, or fold them and bring them aboard if they fit in the overhead bin.
Is there a size limit for personal items on Southwest?
Southwest does not publish a specific size limit for personal items, only that they must fit under the seat in front of you. In practice, anything that fits comfortably under a standard airplane seat — a purse, small backpack, or laptop bag — will pass. If it does not fit under the seat, it will be treated as a carry-on.