What Is Underseat Luggage? Personal Item vs Carry-On, Explained
Underseat luggage is a small bag made to fit in the space under the seat in front of you on a plane. Most airlines call it your personal item. Many underseat bags have wheels and a pull handle, like a mini suitcase, so you can roll them through the airport instead of carrying them.
Personal item vs carry-on
On most flights you can bring two kinds of cabin bag:
- A personal item. This is the small one. It goes under the seat in front of you. Think purse, laptop bag, small backpack or an underseat roller.
- A carry-on. This is the bigger one, usually a small suitcase. It goes in the overhead bin.
The difference matters most on the cheapest fares. On many basic fares, the personal item is the only free bag. The carry-on costs extra, or isn't allowed at all. That's why underseat luggage has become popular: it lets you take more than a backpack without paying for the bin.
One catch: the underseat bag usually is your personal item. You can't normally bring a purse or laptop bag on top of it, so pack those inside.
How big is underseat luggage?
There's no single size. Each airline sets its own rule, and the rules change.
- Many bags are built to about 18 x 14 x 8 inches. That's the size most underseat listings aim for, and you'll see it in product names. It's a common limit, but not every airline uses it.
- Some airlines are smaller. A bag that fits one airline can fail at another, so pack for the strictest airline on your trip.
- Some airlines give no number at all. When we read Southwest's carry-on page, it said only that your personal item should fit under the seat in front of you. Its carry-on size, by contrast, counts wheels, handles and anything attached.
For the numbers each US airline publishes, see our personal item size by airline guide. Always check your airline's own page before you fly.
Wheels and handles count
This is where most people get caught. An airline measures the whole bag, not just the box. Wheels stick out at the bottom, and a pull handle can add height at the top.
Some listings tell you the full size with wheels; others only give the size of the case. If the listing doesn't say the wheels are included, assume they aren't, and leave some room.
What's the largest underseat luggage?
The biggest underseat bags are built right up to about 18 x 14 x 8 inches and hold around 30 liters.
But bigger isn't always better. The space under a seat changes from plane to plane. Seat legs, a box under the seat, or a bulkhead row can all leave you less room. Travelers on forums often say a bag that fit on one flight didn't fit on the next. A bag with an inch to spare fits more planes, and leaves you somewhere to put your feet.
Wheels or a backpack?
Both work as a personal item. The choice comes down to how you travel.
Choose wheels if:
- You walk long distances through airports, or have a bad back or shoulders.
- You also bring a carry-on suitcase. Many underseat rollers have a trolley sleeve: a strap on the back that slides over your suitcase's handle, so you push both bags with one hand.
Choose a backpack if:
- You walk on stairs, cobblestones or busy streets, where wheels are hard work.
- You want every bit of space. Wheels and a handle frame take up room and weight that a backpack uses for packing.
- You might need to squeeze it into a tight space. A soft backpack squashes; a roller doesn't.
If a backpack suits you better, see our personal item backpack comparison.
Spinners or two wheels?
Underseat rollers come with either spinner wheels (four or more that turn in every direction) or two fixed wheels.
- Spinners roll upright beside you and can go sideways down a narrow plane aisle.
- Two fixed wheels roll only when you tilt the bag, so you pull it behind you. They're simpler, but the bag's weight hangs on your arm.
Tips for flying with underseat luggage
- Measure it packed. Soft bags bulge. Stuffing the front pocket is the most common way to go over the depth limit.
- Keep what you need in flight on top. You'll have to pull the bag out from under the seat to reach anything.
- Check the weight too. Some airlines outside the US also weigh cabin bags. Our guide to carry-on weight limits on international flights explains how.
The bottom line: a personal item with wheels
Underseat luggage is a personal item with wheels. It fits under the seat in front of you, travels free on most fares, and rolls so you don't have to carry it. Choose one that states its size with the wheels included, stays under your airline's limit, and has a trolley sleeve if you also bring a suitcase. For five rolling underseat bags compared side by side, see our best underseat luggage.