Linear inches is the sum of your luggage's length, width, and height

Airlines measure luggage size by adding together the longest side, the widest side, and the tallest side of your bag. That total is your linear inches (also called "inches in length and girth"). A bag that is 22 inches long, 14 inches wide, and 9 inches tall has 45 linear inches. Most airlines allow carry-on bags up to 22 inches of linear measurement, and checked bags up to 62 inches, but these limits vary by carrier.

You do not need special tools. A fabric measuring tape or a rigid ruler works equally well. The measurement takes about two minutes and tells you whether your bag will fit in the overhead bin or whether you will need to check it.

Key Takeaways

  • Linear inches means length plus width plus height—measure the three longest dimensions of your bag and add them together.
  • Measure your empty bag, not with clothes inside, so you know the actual bag size rather than how full it is.
  • Measure the outside of the bag, not the inside, because airlines care about the space your bag takes up in the plane.
  • Most carry-on limits are 22 inches and most checked limits are 62 inches, but your specific airline's rules may differ.

What to measure: the three dimensions

Place your bag upright on a flat surface, as if it were sitting in an overhead bin or on the ground. Identify the three measurements you need: the height (top to bottom when standing), the width (left to right), and the depth (front to back). These are the three longest sides of your bag. Wheels, handles, and pockets do not count—measure only the main body of the bag itself.

If your bag has a rounded or curved shape, measure the widest point. For a duffel bag, that means measuring across the fattest part of the roll. For a hard-sided suitcase, measure the flat sides. If your bag has expandable sections, measure it in the expanded position, because that is the size it will be when you pack it.

How to take each measurement accurately

Start with height. Place your measuring tape at the very bottom of the bag (not including wheels or feet) and run it straight up to the highest point of the bag. Write down this number. Do not round up or down yet—record the exact measurement.

Next, measure width. With the bag still upright and facing you, measure from the leftmost edge to the rightmost edge. This is usually the side-to-side distance. Write this down.

Finally, measure depth. This is the front-to-back distance. Place your tape at the front of the bag and measure straight back to the rear. Write this number down as well.

Add all three numbers together. If your measurements are 24 inches (height) + 16 inches (width) + 11 inches (depth), your linear inches total is 51 inches. Round up any partial inches—if you measure 24.5 inches, count it as 25 inches.

Common mistakes that throw off your measurement

The most frequent error is measuring with the bag packed. Your bag's actual size is its empty size. Clothes and items inside make it bulge, which changes the width and depth. Measure the bag as it sits empty so you know the true dimensions.

Another mistake is including wheels or handles in your height measurement. Wheels are not part of the bag's body—they sit underneath. Handles stick up above the bag. Measure only the bag itself, from the bottom of the main compartment to the top of the main compartment, not including anything that sticks out.

Some people measure the inside of the bag instead of the outside. Airlines care about how much space your bag takes up in the plane, which is the outside measurement. The inside is always smaller because of the material thickness.

If your bag has a hard shell, do not measure the bumps or ridges—measure the flat sides. If it has soft fabric, measure the widest point the fabric reaches when the bag is sitting normally.

What to do if your bag exceeds the limit

If your bag is over the carry-on limit (usually 22 inches), you will need to check it instead. Checked baggage usually allows up to 62 inches of linear measurement, so most standard suitcases fit. Check your airline's website for their specific limits, because some carriers have different rules for different ticket types.

If your bag exceeds even the checked limit, you have a few options. You can purchase a smaller bag, pack less, or ship some items separately to your destination. Some airlines charge an oversized baggage fee if your bag is between 62 and 80 inches, so it may be worth calling the airline to ask about fees before you travel.

How different airlines measure luggage

Most major U.S. carriers—including Delta, United, American, and Southwest—use the same linear inch system. However, the size limits differ. Southwest allows 24 inches of linear measurement for carry-on bags. Delta, United, and American allow 22 inches. For checked bags, most allow 62 inches, but some budget carriers or international airlines may have different rules.

If you are flying with a budget airline or an international carrier, check their website before you travel. The airline's baggage policy page will list the exact dimensions they allow. Measuring your bag ahead of time means you will not be surprised at the gate.

Frequently Asked Questions

Do I measure the bag with or without the wheels?

Measure without the wheels. Wheels sit underneath the bag and are not part of the main body. Measure from the bottom of the bag's main compartment (where the wheels attach) to the top. If your bag has feet or a base that sticks out, do not include those either.

What if my bag has an expandable section?

Measure it in the expanded position. If your bag can expand by a few inches, measure it as if it is fully expanded, because that is how large it will be when you pack it. Airlines measure bags as they will actually be used, not in their smallest possible state.

Can I round down if I measure 22.3 inches?

No. Round up. If you measure 22.3 inches, count it as 23 inches. Airlines measure strictly, and rounding down could mean your bag does not fit when you arrive at the airport. It is safer to round up and know your bag will fit.

Do soft-sided bags measure differently than hard-sided bags?

Measure the widest point either way. For soft-sided bags, that is where the fabric bulges most when sitting normally. For hard-sided bags, measure the flat panels. Both methods give you the actual space your bag will take up.

What if the airline's website shows dimensions instead of linear inches?

Add them together yourself. If the airline lists "22 x 14 x 9 inches," add those three numbers: 22 + 14 + 9 = 45 linear inches. Some airlines list dimensions; others list the total linear inches. Either way, you can calculate the linear inches by adding the three numbers.