Linear inches is the sum of your bag's length, width, and depth

Linear inches (also called linear dimensions) is the total you get when you add together the length, width, and depth of your luggage. Airlines use this number to decide whether your bag fits in the overhead bin or counts as oversized. A bag measuring 22 inches long, 14 inches wide, and 9 inches deep has 45 linear inches total (22 + 14 + 9 = 45).

Most airlines allow carry-on bags up to 45 linear inches. Checked bags typically have a limit of 62 linear inches, though this varies by carrier. The measurement matters because it's the standard way the airline industry defines bag size—not weight, not volume, but the three dimensions added together.

Key Takeaways

  • Linear inches is length plus width plus depth; measure the outside of your bag at its widest points in each direction.
  • Most carry-on limits are 45 linear inches; most checked bag limits are 62 linear inches, but confirm with your airline before you pack.
  • Soft-sided bags can compress slightly, so measure them when they're empty and standing upright, not when they're stuffed.
  • If your bag is over the limit, the airline may charge an oversized fee or require you to check it instead of carrying it on.

Measure at the widest point in each direction

Place your bag on a flat surface and measure from the bottom to the top for height. Measure from the left side to the right side for width. Measure from the front to the back for depth. Use a soft measuring tape or a ruler; a hard ruler works if you hold it straight against the bag.

Measure the outside of the bag, not the inside. Include any pockets, handles, or wheels that stick out. If your bag has wheels, measure from the bottom of the wheels to the top of the bag. If it has a handle that extends above the bag, do not include the handle—measure to the top of the bag itself.

For soft-sided bags, measure when the bag is empty and standing upright on a flat surface. Do not squeeze or compress it. Soft bags can shift slightly when packed, so this gives you the most accurate number for what the airline will see.

Write down all three measurements before you add them

Jot down the length, width, and depth on a piece of paper or your phone. Double-check each measurement by measuring again. Then add the three numbers together. This total is your linear inches.

If you are measuring a bag you already own, take a photo of the measurements written down. If you are shopping for a new bag, the manufacturer usually lists the linear inches on the product page or in the specifications—look for "dimensions" or "linear inches" in the details.

Confirm your airline's specific limit before you travel

The 45-inch carry-on and 62-inch checked-bag limits are standard across most major U.S. carriers, but not all airlines follow them. Some budget airlines have smaller limits. Some airlines also charge differently depending on whether your bag is soft-sided or hard-sided, or whether it has wheels.

Visit your airline's website and search for "baggage dimensions" or "bag size limits." The policy page will list the exact measurements allowed for carry-on and checked bags. If you are flying with a bag that is close to the limit—say, 44 or 46 linear inches—call the airline's baggage department before you arrive at the airport. They can tell you whether your specific bag will be accepted.

What happens if your bag exceeds the limit

If your carry-on bag is over 45 linear inches, the airline may ask you to check it instead. You will not be charged a fee for this—it is a standard rerouting. However, you will lose the convenience of having your bag with you during the flight.

If your checked bag is over 62 linear inches, most airlines charge an oversized baggage fee. This fee ranges widely by carrier and can be $50 to $200 or more for a single bag. Some airlines also have a maximum size limit beyond which they will not accept the bag at all, even with a fee. Check your airline's policy to know the hard limit.

Soft-sided bags may compress at security or gate check

A soft-sided bag that measures 45 linear inches when empty might compress slightly as it goes through the security line or when a gate agent handles it. This compression is normal and usually does not cause a problem. However, if your bag is already at or very close to the limit, the compression could push it over in the agent's judgment.

If you have a soft-sided bag that is borderline, pack it a little lighter or choose a slightly smaller bag. Hard-sided bags do not compress, so they are a safer choice if you are right at the limit.

Frequently Asked Questions

Do wheels and handles count toward linear inches?

Wheels count—measure from the bottom of the wheels to the top of the bag. Handles that extend above the bag do not count; measure to the top of the bag itself. Handles that are part of the bag's structure (like a top handle on a duffel) are included in the height measurement.

What if my bag is an odd shape?

Measure the longest point in each direction. If your bag is wider at the bottom than the top, measure the widest point. If it tapers, measure where it is thickest. Use the largest measurement in each dimension to be safe.

Can I measure my bag while it's packed?

No. Measure it empty and standing upright. A packed bag may bulge unevenly and give you a false reading. The airline will see your bag when it is packed, but the standard measurement is taken on an empty bag in its normal shape.

Do I need to measure both my carry-on and checked bag?

Yes, if you are bringing both. Carry-on and checked bags have different size limits. Measure each one separately to make sure both fit within their respective limits.

What if the airline's website does not list dimensions?

Call the airline's baggage department directly. They can tell you the exact limits and whether your specific bag will be accepted. Having this conversation before you arrive at the airport saves time and stress.