Linear inches is the sum of your bag's length, width, and height added together

Airlines measure luggage using linear inches (also called inches of girth) because it accounts for overall size, not just weight. To find your bag's linear inches, measure the length, width, and depth in inches, then add those three numbers. A bag that is 22 inches long, 14 inches wide, and 9 inches deep totals 45 linear inches. That single number is what airlines compare against their size limits.

Most airlines set a limit of 62 linear inches for checked bags and 45 linear inches for carry-on bags, though some budget carriers are stricter. Knowing your bag's linear inches before you pack tells you whether it will fit in the overhead bin or if you will have to check it—and whether you might face an oversized baggage fee.

Key Takeaways

  • Linear inches equals length plus width plus depth; measure all three dimensions and add them together.
  • Use a soft measuring tape along the outside of the bag, including any handles or wheels that stick out.
  • Most airlines allow 62 linear inches for checked bags and 45 for carry-on, but verify your airline's specific limits before packing.
  • If your bag is close to the limit, measure it when empty and again when packed, because soft-sided luggage can expand.

What to measure and where to start

Measure the bag itself, not the contents. Place the luggage on a flat surface and measure from the lowest point to the highest point for length (usually the longest side). Then measure the width (side to side) and depth (front to back). Include any permanent attachments—wheels, handles, or pockets that stick out—in your measurements. If a handle folds down, measure it in the position it will be in when you travel.

Use a soft measuring tape or a piece of string and a ruler, not a rigid ruler that will not bend around corners. Measure to the nearest half-inch. If your bag is 22.3 inches, round to 22.5 inches; if it is 22.7 inches, round to 23 inches. Airlines round up, so it is better to overestimate slightly than to arrive at the airport and discover your bag is larger than you thought.

Soft-sided versus hard-sided luggage

Soft-sided bags (made of fabric or nylon) can compress and expand depending on how full they are. Measure a soft-sided bag when it is empty and again when it is packed to the way you actually travel. If it expands by an inch or two when full, use the packed measurement to check against airline limits. Hard-sided luggage (plastic or aluminum) does not change size, so one measurement is enough.

Some travelers measure soft-sided bags at their maximum expansion to be safe. If your empty bag measures 44 linear inches but expands to 46 when packed, and your airline's carry-on limit is 45, you will need to check it or pack lighter. It is better to know this before you arrive at the gate.

Finding your airline's specific size limits

The 62-inch limit for checked bags and 45-inch limit for carry-on bags are common, but not universal. Budget airlines like Spirit and Frontier often set lower limits—sometimes 40 inches for carry-on. International carriers may differ from domestic ones. Check your airline's website under "baggage" or "luggage" and look for the section on dimensions or size restrictions.

Write down the limits for both checked and carry-on bags. Some airlines charge a fee if your checked bag exceeds the size limit (separate from weight fees), and oversized carry-on bags are often gate-checked for free, but you lose the convenience of having your bag with you. Knowing the limits ahead of time lets you choose which bag to use or whether to pack differently.

How to record and remember your measurements

Once you have measured your bags, write the linear inches on a small label or piece of tape and stick it inside the bag, or keep a note on your phone. Include the date you measured it, especially for soft-sided bags that may change over time. If you own multiple bags, label each one with its linear inches so you can grab the right size for each trip without remeasuring.

You can also take a photo of the measurement tape against your bag and save it in your phone's photos. When you are packing for a trip, you can quickly check whether your chosen bag will work for that airline's limits without having to measure again.

What happens if your bag exceeds the limit

If your bag is larger than the airline's carry-on limit, it will be gate-checked—taken from you at the boarding gate and loaded into the cargo hold. You will get it back when you land. This is usually free, but it means you cannot access anything in that bag during the flight.

If your checked bag exceeds the size limit (not the weight limit, which is separate), you may be charged an oversized baggage fee, typically $50 to $100 depending on the airline. Some airlines do not charge for oversized checked bags as long as they are under a certain weight; others charge for size regardless of weight. A few airlines refuse to take bags over a certain size at all. Measuring before you pack prevents surprises at the counter.

Frequently Asked Questions

Do I measure the bag with or without the handle extended?

Measure the bag in the position it will be in when you travel. If the handle folds down flat against the bag, measure it folded. If it stays extended, measure it extended. Wheels and fixed handles that stick out should always be included in your measurement.

What if my bag has an expandable section?

Measure the bag in its normal, non-expanded state. If you plan to use the expandable section, measure it expanded. Most airlines allow the expansion as long as the total linear inches stays within their limit, but check your airline's policy to be sure.

Can I measure in centimeters and convert?

Yes. One inch equals 2.54 centimeters. Measure in centimeters, add the three dimensions, then divide by 2.54 to get linear inches. Rounding to the nearest half-inch is still a good idea to stay safe.

Do I need to measure my bag every time I travel?

No. Once you have measured a hard-sided bag, the size does not change. For soft-sided bags, remeasure if you pack significantly heavier or lighter than usual, or once a year to account for wear. Otherwise, one measurement per bag is enough.

What if the airline's website does not list size limits?

Call the airline's customer service line or use their online chat. They can tell you the exact limits for your flight. Some airlines list limits by cabin class (economy, business) or by route, so it is worth asking specifically about your trip.