What linear inches means and why airlines care

Linear inches is the sum of your luggage's length, width, and height added together. Airlines use this number to decide whether your bag fits in the overhead bin or under the seat in front of you. A bag measuring 22 inches long, 14 inches wide, and 9 inches deep adds up to 45 linear inches total.

Most airlines allow carry-on bags up to 22 inches long, 14 inches wide, and 9 inches deep—which totals 45 linear inches. Checked bags usually have a limit of 62 linear inches. If your bag exceeds the limit, you may be charged an oversized baggage fee or forced to check a carry-on at the gate. Different airlines set different limits, so checking your airline's policy before you travel saves money and hassle.

Key Takeaways

  • Linear inches is the length plus width plus height of your bag, measured in a straight line on each dimension.
  • You need a soft measuring tape or a rigid ruler to get accurate measurements; a tape measure works best for soft-sided luggage.
  • Measure the widest, tallest, and deepest points of your bag when it is empty and sitting flat on a surface.
  • Most carry-on limits are 45 linear inches, but check your specific airline's policy because limits vary.
  • Soft-sided bags may compress slightly when packed, but airlines measure the bag's maximum dimensions, not the packed size.

Gather the right measuring tools

You need either a soft measuring tape (the kind tailors use) or a rigid ruler or yardstick. A soft measuring tape is easier because it conforms to the shape of your luggage and gives you a straight reading without gaps. If you use a rigid ruler, you will need to hold it flush against the bag and read the number where the edge ends.

Avoid measuring with a string and then measuring the string later—the string can stretch or shift, and you will lose accuracy. A measuring tape from a hardware store or a cloth tape from a sewing kit both work well. Make sure the tape is marked in inches, not centimeters, unless you plan to convert.

Measure length, width, and height correctly

Place your empty bag on a flat surface like a table or the floor. Stand it upright in the position you would carry it or check it. Measure from the bottom to the top—that is your height. Measure from the left side to the right side—that is your width. Measure from the front to the back—that is your depth (sometimes called length).

Measure at the widest, tallest, and deepest points of the bag. If your bag has wheels, measure from the bottom of the wheels to the top of the bag. If it has a handle, do not include the handle in the height measurement—measure only the bag itself. Round up to the nearest half inch if your measurement falls between numbers. A bag that measures 21.3 inches should be counted as 21.5 inches.

For soft-sided luggage, press gently on the sides while measuring to find the true outer dimensions. Do not squeeze hard—you are looking for the bag's normal shape, not its compressed shape. Hard-sided luggage is simpler because the dimensions are fixed and obvious.

Add the three measurements together

Once you have your three numbers, add them. If your bag is 22 inches long, 14 inches wide, and 9 inches deep, the math is 22 + 14 + 9 = 45 linear inches. Write down the total and keep it with your travel documents or take a photo of your measurements on your phone.

If you are buying a new bag and the tag lists dimensions, you can add those numbers without measuring. Luggage manufacturers always list dimensions in length × width × depth order. A bag labeled "22 × 14 × 9" already tells you it is 45 linear inches.

Check your airline's specific limits

Visit your airline's website and search for "carry-on baggage dimensions" or "checked baggage dimensions." Most major carriers (United, American, Delta, Southwest) allow 45 linear inches for carry-on and 62 linear inches for checked bags, but some budget airlines are stricter. Spirit and Frontier, for example, limit carry-on bags to 40 linear inches unless you pay an extra fee.

If you are flying internationally, the limit may be different. European carriers often use centimeters instead of inches. Write down your airline's limit before you pack so you know whether your bag will fit. If your bag is close to the limit—say, 44 or 46 linear inches—measure it twice to be sure.

What to do if your bag exceeds the limit

If your bag is over the limit, you have a few options. You can check it instead of carrying it on, if you are willing to pay a checked baggage fee and wait at baggage claim. You can buy a smaller bag that fits the limit. You can remove items and pack them in a personal item (a purse, backpack, or small crossbody bag) that fits under the seat in front of you.

Some travelers try to compress soft-sided bags by sitting on them or rolling them tightly. This works temporarily, but airlines measure bags in their normal state, not compressed. If a gate agent measures your bag and it exceeds the limit, you will be charged or asked to check it, even if you packed it small. Packing light from the start is the safest approach.

Frequently Asked Questions

Do wheels and handles count toward linear inches?

Wheels do count—measure from the bottom of the wheels to the top of the bag. Handles do not count. Measure only the bag itself, not the extended handle. Some bags have handles that fold into the bag; measure the bag in its normal carrying position.

Should I measure my bag when it is packed or empty?

Measure it empty. Airlines measure the bag's maximum dimensions, not how full it is. An empty bag gives you the true outer size. If your packed bag bulges larger than the empty bag, it may exceed the limit when you try to board.

Can I measure in centimeters and convert to inches?

Yes. One inch equals 2.54 centimeters. If your tape measure shows centimeters, divide by 2.54 to get inches. For example, 56 centimeters ÷ 2.54 = 22 inches. Round to the nearest half inch for safety.

What if my bag has an expandable section?

Measure the bag in its expanded position if you plan to use the expansion. Airlines measure bags as they are presented at check-in or the gate. If the bag is expanded, that is the size they will measure.

Do different airlines measure the same way?

Yes. All airlines measure length, width, and height and add them together. The limits differ between airlines, but the method is the same. Once you know your bag's linear inches, you can check it against any airline's policy.