The standard carry-on size across most airlines

Most major airlines in the United States allow a carry-on bag measuring 22 inches long, 14 inches wide, and 9 inches deep. This is the size limit set by the International Air Transport Association (IATA), which most carriers follow. Your bag must fit in the overhead bin or under the seat in front of you without being forced or compressed.

The actual limit varies slightly by airline. Southwest, American, Delta, and United all use the 22 × 14 × 9 inch standard. Budget carriers like Frontier and Spirit sometimes enforce stricter limits—Frontier allows 22 × 18 × 10 inches, which sounds larger but is actually measured differently. Always check your specific airline's website before you pack, because the difference between what fits and what doesn't can mean checking a bag at the gate and paying a fee.

Weight limits for carry-on bags are less standardized. Most airlines don't officially weigh carry-on luggage, but if a bag is so heavy you can't lift it into the overhead bin yourself, a gate agent can refuse it. Some airlines like Southwest and Alaska do list weight limits (50 pounds), but enforcement is inconsistent.

Key Takeaways

  • The standard carry-on size is 22 × 14 × 9 inches, which fits in overhead bins on most aircraft.
  • Each airline sets its own limits, so a bag that works on one carrier might not work on another—check before you book.
  • Airlines measure carry-on bags by length, width, and depth, and your bag must close without forcing the lid or sides.
  • If your bag doesn't fit in the overhead bin or under the seat during boarding, the airline can check it at the gate and charge you a fee.

How airlines measure your bag

Airlines measure carry-on luggage by adding the length, width, and depth together—a method called linear inches. A 22 × 14 × 9 inch bag totals 45 linear inches. Some airlines, particularly budget carriers, use this total instead of individual dimensions. Frontier, for example, allows bags up to 48 linear inches, which gives you a bit more room in one direction if you're willing to sacrifice it in another.

The measurement matters because a bag that's 24 inches long but only 12 inches wide and 8 inches deep (44 linear inches) might fit in the overhead bin even though it exceeds the length limit. However, most gate agents measure the three dimensions separately, not the total, so staying under 22 × 14 × 9 is the safest approach.

Soft-sided bags are easier to squeeze into tight spaces than hard-sided ones. If your bag is close to the limit, a soft-sided roller or duffel will compress slightly and fit where a rigid suitcase won't. This is why many frequent travelers prefer soft luggage for carry-on.

What happens if your bag is too large

If your bag doesn't fit in the overhead bin or under the seat during boarding, the airline will gate-check it—meaning they'll take it at the gate and load it into the cargo hold. You'll retrieve it when you land. Gate-checked bags are usually free if the flight is full and overhead space runs out, but if your bag is oversized, you may be charged a checked baggage fee, which ranges from $25 to $50 depending on the airline.

The risk of gate-checking increases on smaller aircraft and full flights. Regional jets and turboprops have smaller overhead bins than wide-body planes. If you're flying a route served by a smaller aircraft, bring a bag you're confident will fit, or plan to check it from the start.

Some airlines, like Spirit and Frontier, charge for carry-on bags that don't fit their size restrictions, even if space is available. Read the fine print on your airline's website to know whether oversized carry-on fees explore to your ticket type.

Personal items versus carry-on bags

Most airlines allow two items in the cabin: a carry-on bag and a personal item. The personal item—typically a backpack, purse, or small roller—must fit under the seat in front of you. There's no official size limit for personal items on most airlines, but if it doesn't fit under the seat, it will be treated as a carry-on.

This distinction matters because if you're traveling light, you can often bring only a personal item and avoid the carry-on size limit altogether. A standard backpack or messenger bag counts as a personal item on every major airline. If you're packing a roller bag as your personal item, make sure it's small enough to slide under a standard airplane seat, which is roughly 17 inches wide and 8 inches tall.

Carry-on rules for specific airlines

Southwest Airlines allows one carry-on bag and one personal item at no extra charge. The carry-on limit is 24 × 16 × 10 inches, which is slightly larger than the IATA standard. Weight limit is 50 pounds.

American, Delta, and United all use the 22 × 14 × 9 inch limit for basic economy and higher fares. They allow one carry-on and one personal item. Some basic economy fares on United don't include a carry-on bag, only a personal item, so check your ticket.

Frontier charges for carry-on bags on most fares. The limit is 22 × 18 × 10 inches. If you buy the "Standard" fare or higher, a carry-on is included. On lower fares, you pay $30 to $50 to bring a carry-on bag.

Spirit Airlines also charges for carry-on bags on base fares. The limit is 22 × 18 × 10 inches. A personal item is free; a carry-on bag costs $35 to $50 depending on when you purchase it.

Alaska Airlines allows one carry-on and one personal item at no charge. The limit is 22 × 14 × 9 inches, with a 50-pound weight limit.

How to measure your own bag

Use a soft measuring tape or a ruler. Measure from the furthest point on each side: the length from the handle to the bottom, the width from side to side, and the depth from front to back. If your bag has wheels, measure from the top of the wheels to the top of the bag. If it has an extending handle, measure with the handle retracted.

Round up to the nearest inch. If your bag measures 21.8 inches long, call it 22 inches. Most gate agents will do the same, and you want to know whether your bag is actually within limits before you reach the airport.

If you're buying a new bag, look for one labeled "carry-on approved" or "IATA compliant." These are designed to fit the 22 × 14 × 9 inch standard. Brands like Away, Coolife, and Samsonite make bags specifically sized for this limit.

International carry-on rules

International flights operated by U.S. airlines follow the same carry-on limits as domestic flights. However, if you're flying on a foreign airline, the rules may differ. European carriers like Lufthansa and Air France often allow 22 × 18 × 10 inches. Asian carriers vary widely—some allow larger bags, others smaller.

If you're connecting through multiple airlines or countries, use the smallest limit in your itinerary. Your bag needs to fit on every flight, including the smallest aircraft you'll board. Check each airline's website before you book.

Frequently Asked Questions

Can I bring a roller bag and a backpack as my carry-on and personal item?

Yes. The roller bag counts as your carry-on, and the backpack counts as your personal item, as long as the backpack fits under the seat. You can bring both on every major airline.

Do I need to remove my carry-on bag from the overhead bin before takeoff?

No. Your carry-on stays in the overhead bin during the flight. You only need to remove it before landing or if the flight attendant asks you to move it to make room for someone else's bag.

What if my bag fits the size limit but is very heavy?

If you can lift it into the overhead bin yourself, most airlines won't weigh it. If a gate agent thinks it's too heavy to safely store overhead, they can refuse it or ask you to check it. This is rare but more common on international flights.

Are hard-sided suitcases or soft-sided bags better for carry-on?

Soft-sided bags compress slightly and fit into tight overhead bins more easily. Hard-sided bags protect contents better but take up more space. For carry-on, soft-sided is usually the better choice if you're close to the size limit.

Do I have to pay extra if my carry-on bag is slightly oversized?

Not if it fits in the overhead bin or under the seat. If it doesn't fit and the flight has room, it will be gate-checked for free. If the flight is full or the airline charges for oversized carry-on bags, you'll pay a fee—usually $25 to $50.