How to Calculate a Carry-On Bag Size

With more and more airlines charging for even your first checked bag, traveling with just a carry-on has become a valuable skill for flyers. But no amount of schmoozing will make that oversize suitcase fit into the bag sizer at the airline gate. If your bag doesn't fit into the sizer – a frame made of metal tubing – it can't travel in the cabin with you. So before you set out with high hopes of a bag-fee-free flight, take a minute before you leave home to measure your carry-on bag and figure out if it meets your airline's size regulations.

Although size limits for checked bags are fairly standardized across airlines, the regulations for carry-on bags can vary a little more, so always check your airline's website for specific sizing guidelines. That said, most airlines will allow one "full-size" carry-on bag that measures 22 to 24 inches high, 14 to 17 inches across and 9 or 10 inches deep.

In order to make sure your bag fits, you'll have to measure each dimension – length, width and height – individually. Make sure you measure each dimension at its widest point. For example, if your carry-on bag is tapered at the top or bottom for stability, measure it from side-to-side at the widest point to determine its width. If exterior pockets bulge to the front when your bag is packed, measure the widest part of that bulge when determining the bag's depth (its measurement from front to back).

And although some luggage manufacturers tell you not to include your bag's wheels or handle in the vertical, top-to-bottom measurement, you'd better include them – otherwise it might not fit into the airplane's overhead compartment.

Although it's rare, some airlines will give their carry-on sizing requirements in linear inches. "Linear inches" simply means the sum total of your bag's length, width and height. So if your airline allows carry-on bags that measure up to 45 linear inches, and your bag measures 20 inches by 10 inches by 9 inches, its measurement in linear inches is 20 + 10 + 9 = 39 inches, so it would be allowed.

Most airlines also allow you to carry on one small personal item, like a purse, briefcase or diaper bag. While airlines occasionally give specific sizing guidelines for these items, most simply require that whatever it is fits entirely underneath the seat in front of you.

Tip

Even if your carry-on bag is the right size, you won't get far if you try to bring prohibited items onto the plane. So take a second to review what you can and can't bring on a plane with you.