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

To find the linear inches of a piece of luggage, measure the length, width, and depth of the bag in inches, then add those three numbers together. That total is your linear inch measurement. Airlines use this number—sometimes called "linear dimensions" or "inches of girth"—to decide whether a bag fits in the overhead bin or counts as checked luggage, and whether it will cost extra.

The measurement matters because airlines have size limits, not weight limits alone. A bag can be light but too large to bring on board. Knowing your bag's linear inches before you pack saves you from surprises at the gate.

Key Takeaways

  • Measure length, width, and depth in inches, then add them together to get linear inches.
  • Most airlines allow carry-on bags up to 22 inches of linear dimensions; checked bags typically go up to 62 inches.
  • Measure the bag when it is empty and at its normal shape, not when stuffed or compressed.
  • Different airlines have different limits, so check your carrier's policy before packing.
  • A soft-sided bag may measure smaller when empty than when full, so account for how you actually pack it.

How to measure your bag correctly

Use a tape measure or ruler and measure in a straight line from the farthest points on each dimension. For length, measure from the top of the bag to the bottom. For width, measure from the left side to the right side. For depth, measure from the front to the back. Round up to the nearest whole inch if you get a decimal—a bag that measures 21.5 inches becomes 22 inches.

Measure the bag when it is empty and sitting in its normal upright position. Do not compress it or squeeze it to make it smaller. If your bag has wheels, measure from the bottom of the wheels to the top of the bag, because the wheels are part of the bag's footprint. If it has a handle that extends above the main body, measure to the top of the handle.

Soft-sided bags (made of fabric) will measure differently when empty versus when packed full. If you plan to fill the bag completely, measure it after packing it the way you normally would. This gives you a realistic sense of whether it will fit the airline's limits.

Common airline size limits and what they mean

Most major U.S. airlines allow carry-on bags up to 22 linear inches. Some allow up to 24 inches. Checked bags typically max out at 62 linear inches, though a few airlines go up to 80 inches for larger checked bags. Budget airlines often have stricter limits—some allow only 18 inches for carry-on.

These limits exist because overhead bins have fixed dimensions. A bag that measures 22 × 14 × 9 inches (45 linear inches total) will fit in most overhead bins. A bag that measures 24 × 16 × 11 inches (51 linear inches) may not, even though it is only 6 inches larger in total, because the shape matters too.

Checked bag limits are higher because they go in the cargo hold, which has more space. However, some airlines charge extra for bags over 50 linear inches, and a few charge for any checked bag at all. Always check your specific airline's website before you pack.

What happens if your bag exceeds the limit

If your carry-on bag is too large, the airline will gate-check it—send it to the cargo hold for free, or charge you a checked bag fee depending on the airline. If your checked bag exceeds the size limit, you may pay an oversized bag fee, which ranges from $50 to $200 depending on the airline and how far over the limit you are.

Some airlines measure bags at the gate using a sizer frame—a metal or plastic box in the exact dimensions allowed. If your bag does not fit through the frame, it does not go in the overhead bin. Soft-sided bags are more forgiving because they can compress slightly, but hard-sided bags cannot.

The best strategy is to measure before you pack and know your airline's policy. If you are close to the limit, choose a smaller bag or pack less. Buying a bag that is slightly under the limit gives you room to pack without worrying.

Comparing hard-sided and soft-sided bags

Hard-sided bags (plastic or aluminum) have fixed dimensions. What you measure is what you get—they do not compress. If a hard-sided bag measures 24 inches and your airline allows 22 inches, it will not fit, and you will pay a fee or have it checked.

Soft-sided bags (fabric with flexible walls) can compress slightly, which sometimes lets them squeeze through a sizer frame even if they measure slightly over the limit. However, do not rely on this. Measure your soft-sided bag when it is packed the way you plan to travel, and use that measurement to decide whether it will work.

For frequent travelers, a soft-sided carry-on bag that measures just under 22 inches offers flexibility. For one-time travelers or people who pack heavy, a hard-sided bag is more predictable because you know exactly what you are getting.

Using a luggage scale and sizer together

Some airports and luggage stores have sizer frames you can use for free before you travel. These frames are the exact dimensions airlines allow, so you can physically test whether your bag fits. If you are buying a new bag and want to be certain, visit a luggage store and ask to test your bag in their sizer.

A luggage scale tells you weight; a tape measure tells you linear inches. You need both pieces of information because airlines enforce both limits. A bag can be under the weight limit but over the size limit, or vice versa. Knowing both numbers means you will not be surprised at the airport.

Frequently Asked Questions

Do I measure the bag with the handle and wheels included?

Yes. Measure from the bottom of the wheels to the top of the handle (or the top of the bag if the handle does not extend above it). The wheels and handle are part of the bag's overall footprint and count toward the linear inches.

What if my bag is soft-sided and changes shape when I pack it?

Measure it after you pack it the way you normally travel. This gives you the real measurement you will face at the airport. If it measures over the limit when packed, you will need to remove items or choose a smaller bag.

Can I round down if my bag measures 22.4 inches?

No. Always round up. A bag that measures 22.4 inches should be counted as 23 inches. Airlines round up to be safe, and you should too when deciding whether your bag fits their limits.

Do different airlines measure bags differently?

No. The measurement method is the same everywhere—length plus width plus depth. However, the size limits vary by airline and by cabin class. A bag that fits on one airline might not fit on another, so always check your specific carrier's policy.

Is there a standard carry-on size?

No single standard exists, but most major U.S. airlines allow 22 linear inches for carry-on. Some allow 24 inches. International airlines and budget carriers may have different limits. Check your airline's website or call them before you buy a bag.