Luggage dimensions are measured in inches or centimeters, length plus width plus height, and that total is what airlines and bag makers call the "linear dimension" or "linear inch"

When you see a suitcase labeled 22 × 14 × 9 inches, those three numbers are length, width, and depth. Add them together: 22 + 14 + 9 = 45 linear inches. That single number — 45 — is what matters to airlines. Most carriers allow carry-on bags up to 22 linear inches; checked bags usually max out at 62 to 80 linear inches depending on the airline.

The measurement itself is straightforward: place the bag on a flat surface, measure from the furthest point on one end to the furthest point on the other end (that is your length), then measure the widest part (width), then measure the tallest part (height). Round up to the nearest inch or centimeter. Wheels, handles, and pockets that stick out count toward the total.

Key Takeaways

  • Luggage size is the sum of length plus width plus height, measured in inches or centimeters, and airlines call this total the "linear dimension."
  • Carry-on bags are typically limited to 22 linear inches; checked bags range from 62 to 80 linear inches depending on your airline.
  • Wheels, handles, and any protruding pockets are included in the measurement, so measure the bag as it sits fully assembled.
  • Different airlines have different size limits, so check your carrier's website before you buy or pack.
  • A soft-sided bag may compress slightly, but you should measure it in its normal, unpacked state.

Why airlines measure this way

Airlines use linear dimensions because they need to know whether a bag will fit in the overhead bin or under the seat in front of you. An overhead bin on most aircraft is roughly 22 × 14 × 9 inches — the exact dimensions that produce 45 linear inches. If your carry-on exceeds that, it will not fit, and you will be asked to check it at the gate.

For checked bags, the airline needs to know the bag will fit through the baggage handling system and into the cargo hold. A bag that is 30 × 20 × 15 inches (65 linear inches) will fit; one that is 32 × 22 × 16 inches (70 linear inches) might not, depending on the aircraft type. That is why the limit exists.

How to measure your own bag

Lay the bag flat on the ground or a table. Use a measuring tape or ruler, and measure from the very bottom to the very top (height), from one side to the other (width), and from front to back (length). If the bag has wheels, include them in the height measurement. If it has a handle that sticks up, measure to the top of the handle.

Write down all three numbers. Add them together. That total is your linear dimension. If you get 45.5 inches, round up to 46. Airlines measure strictly, and a bag that is even half an inch over the limit can be rejected.

If your bag is soft-sided (made of fabric rather than hard plastic), measure it in its normal state, not compressed. Do not squeeze it down to make it smaller — the airline will measure it the same way you did, and if it expands during packing, it may exceed the limit when you arrive at the airport.

Carry-on versus checked bag limits

Most U.S. airlines allow carry-on bags up to 22 linear inches. Some budget carriers like Southwest and Spirit are stricter and cap carry-ons at 18 or 20 linear inches. International carriers vary widely; some allow 45 linear inches for carry-on, others allow 55.

Checked bags are almost always larger. Standard limits are 62 linear inches (common on domestic flights) to 80 linear inches (common on international flights). Some airlines charge extra if your checked bag exceeds 62 inches but stays under 80. A few charge for any checked bag at all, regardless of size.

Weight matters separately from size. Even if your bag is within the linear dimension limit, it may be too heavy. Most airlines allow 50 pounds for checked bags and 25 pounds for carry-on, though these limits vary. Check your airline's website for both size and weight rules before you pack.

What happens if your bag is too large

If your carry-on exceeds the limit, the airline will ask you to check it at the gate. You will lose the convenience of keeping it with you, and if you are on a tight connection, your bag might not make it to your next flight. If your checked bag exceeds the limit, you may be charged an oversized baggage fee, which ranges from $50 to $200 depending on the airline and how much you exceed the limit.

Some airlines will refuse to accept a bag that is far over the limit, even with a fee. If your bag is 90 linear inches, no airline will take it as checked luggage. In that case, you will need to ship it separately or buy a smaller bag.

Measuring bags with unusual shapes

A duffel bag or a backpack is measured the same way: length, width, height. Lay it flat, measure the longest dimension, the widest dimension, and the tallest dimension. If it has straps or pockets that stick out, include them.

A rolling suitcase is straightforward: measure from the bottom of the wheels to the top of the handle (height), side to side (width), and front to back (length). A garment bag is measured flat: length (top to bottom when hanging), width (side to side), and depth (front to back when folded).

If your bag has a shape that makes it hard to measure — say, a rounded top or tapered sides — measure the widest and tallest points. Airlines will do the same.

Soft-sided versus hard-sided bags

Hard-sided bags (polycarbonate or ABS plastic) hold their shape and will measure the same every time. Soft-sided bags (nylon or canvas) can compress, which means they might measure smaller when empty and larger when packed. Measure a soft-sided bag in its normal, unpacked state, as if it were sitting in your closet ready to use.

If you are buying a new bag and want to be certain it will fit, look for one that is at least an inch smaller in each dimension than the airline's limit. A carry-on rated at 21 × 13 × 8 inches (42 linear inches) will fit comfortably in a 22 × 14 × 9 inch space. A checked bag rated at 28 × 18 × 12 inches (58 linear inches) will fit in a 62-inch limit with room to spare.

Frequently Asked Questions

Do wheels count toward the luggage size?

Yes. Wheels are part of the bag, so measure from the bottom of the wheels to the top of the bag. If your suitcase is 22 inches tall with wheels, that 22 inches includes the wheel height. The same applies to handles: measure to the top of the handle.

Can I compress my soft bag to make it smaller?

You can compress it to pack it, but measure it in its normal state before you pack. Airlines will measure it as it sits on the scale, and if it expands during travel, it may exceed the limit. Compression bags can help, but the airline's limit is based on the bag's actual dimensions, not a compressed version.

What if my bag is exactly 22 inches on one side?

If your total linear dimension is exactly 45 inches (or whatever the limit is), you are at the threshold. Most airlines will accept it, but some measure strictly and may reject a bag that is exactly at the limit. To be safe, aim for at least half an inch under the maximum.

Do different airlines measure differently?

All airlines use the same method — length plus width plus height — but their limits vary. Southwest allows 24 × 16 × 10 inches for carry-on (50 linear inches), while most other U.S. carriers allow 22 × 14 × 9 inches (45 linear inches). Always check your specific airline's website before you travel.

Is there a tool or app that helps measure luggage?

A measuring tape and a calculator are all you need. Some luggage brands print the dimensions on a tag attached to the bag, so check there first. If you are buying a bag online, the product page will list the dimensions. Measure your own bag the same way: length, width, height, add them together.