Measure length, width, and depth with a tape measure or ruler
Airlines measure luggage by adding together the length, width, and depth of your bag — a total called the linear dimension or linear inch. You need a soft tape measure or a rigid ruler. Measure the longest point of each side: the height when the bag is standing upright, the width from left to right, and the depth from front to back. Write down all three numbers.
Most airlines allow carry-on bags up to 22 inches long, 14 inches wide, and 9 inches deep — which adds up to 45 linear inches. Checked bags are usually limited to 62 linear inches total. Some airlines are stricter: Southwest, for example, caps carry-on at 24 x 16 x 10 inches (50 inches total). Budget carriers like Frontier and Spirit often charge for any bag larger than a personal item, which is typically 18 x 14 x 8 inches (40 inches).
Key Takeaways
- Measure the length, width, and depth of your bag at its widest points, then add the three numbers together to get the linear dimension.
- Most major airlines allow carry-on bags up to 45 linear inches and checked bags up to 62 linear inches, but budget carriers and some international airlines have smaller limits.
- Check your specific airline's website before you pack, because size limits vary by carrier and sometimes by ticket type.
- If your bag is close to the limit, pack lighter to compress it, or measure it again after packing to confirm it still fits.
Where to find your airline's size limits
Every airline publishes its baggage policy on its website. Look for a page labeled "Baggage," "Checked Baggage," or "Carry-On Policy." The policy will list the maximum dimensions for carry-on and checked bags, and sometimes for personal items as well. If you booked through a third-party site like Kayak or Expedia, go directly to your airline's website instead — third-party sites sometimes show outdated information.
Size limits can change based on your ticket type. Basic economy fares on United, American, and Delta often include only a personal item, not a full carry-on. First-class and premium cabin passengers may have higher limits. If you are unsure which ticket type you bought, check your confirmation email or log into your airline account.
Measure your bag before you pack it
An empty bag is easier to measure accurately than a full one. Lay the bag flat on a table or floor, extend any handles or wheels, and measure from the outside edge. If your bag has wheels, measure from the bottom of the wheels to the top of the bag. If it has a handle, measure from the bottom to the top of the handle when it is fully extended.
Soft-sided bags compress, so an empty measurement may not tell you the full story. After you pack, measure again. If the bag is now larger than the airline's limit, remove items or switch to a smaller bag. Hard-sided luggage does not compress, so one measurement usually holds.
What happens if your bag is too large
If your carry-on is oversized, the gate agent will ask you to check it at the gate. You will not pay a fee on most airlines, but your bag will arrive at your destination on the same flight, not with you. If your checked bag exceeds the size limit, most airlines charge an oversize fee of $50 to $100 per bag, depending on the carrier.
Budget airlines enforce size limits more strictly. Frontier, Spirit, and Allegiant will not let you bring a carry-on larger than their stated dimensions without paying a fee. On these carriers, measure carefully and pack accordingly.
Use a luggage scale and a sizer frame if you want to be certain
Many airports have luggage sizers — metal frames at check-in that show whether your bag fits the airline's dimensions. If your bag fits inside the frame, it meets the size requirement. Some travelers buy a personal luggage sizer online for $15 to $30 to test their bags at home before heading to the airport.
A luggage scale is separate from a sizer but equally useful. Airlines also charge overweight fees — usually $25 to $75 per bag — if your checked luggage exceeds 50 pounds. A home scale lets you weigh your bag before you leave, so you can remove items if needed. Digital luggage scales are available for $10 to $25.
Common size limits by airline type
| Airline Type | Carry-On Limit | Checked Bag Limit |
|---|---|---|
| Major U.S. carriers (American, Delta, United) | 22 x 14 x 9 inches (45 linear inches) | 62 linear inches |
| Southwest | 24 x 16 x 10 inches (50 linear inches) | 62 linear inches |
| Budget carriers (Frontier, Spirit, Allegiant) | 18 x 14 x 8 inches (40 linear inches) — often charged | 62 linear inches |
| International carriers (varies) | 22 x 14 x 9 inches or smaller | 62 to 70 linear inches |
Frequently Asked Questions
Do wheels and handles count toward the size limit?
Yes. Measure from the outermost point of the wheels or handle. A bag that is 20 inches tall without wheels may be 22 inches with them. Airlines measure the total footprint of the bag as it sits, so include any protruding parts.
What if my bag is soft-sided and compresses?
Measure it empty first, then pack it and measure again. If it exceeds the limit when full, remove items or use a smaller bag. Gate agents will compress soft bags slightly to fit them in the overhead bin, but they will not accept a bag that is clearly oversized.
Can I bring both a carry-on and a personal item?
Most airlines allow one carry-on plus one personal item (purse, backpack, or small bag). The personal item is usually limited to 18 x 14 x 8 inches. Check your airline's policy, because budget carriers sometimes charge for a carry-on and only include a personal item with the base fare.
Do I need to measure my bag if I am flying internationally?
Yes. International airlines often have smaller carry-on limits than U.S. carriers — sometimes as small as 21 x 13 x 8 inches. Check your specific airline's website before you pack, because limits vary widely by carrier and destination.
What is the difference between linear inches and cubic feet?
Linear inches add the three dimensions together (length + width + depth). Cubic feet multiply them (length × width × depth). Airlines use linear inches for luggage. You will see cubic feet used for cargo or storage space, not passenger baggage.