How to Assess Luggage Linear Dimensions

Nothing matches the sadness – and financial hurt – of hauling your carefully packed checked luggage up to the airline counter, only to see it slapped with an "oversize" label and the according fees. Depending on your airline, these fees can run into the triple digits. Even though it won’t get you slapped with baggage fees, the same hurt can be felt if you realize your carry-on luggage is too large to take onto the flight, causing a whole host of other problems.

That said, all major airlines make their luggage sizing requirements clear on their websites, usually in terms of linear inches. So, you can save a lot of money by taking a few minutes to measure your bag before heading out to your flight.

Linear inches – or really, any linear dimension – simply refer to the sum total of your bag's length, width and depth. So, if your bag measures 28 inches high, 13 inches wide and 10 inches deep, its linear measurement or linear dimensions would be 28 + 13 + 10 = 51 linear inches. If your bag measures 25 inches high, 14 inches wide and 12 inches deep, its total linear dimensions would be 25 + 14 + 12 = 51 linear inches.

As you might notice, using linear dimensions for size regulations is a handy way for airlines to allow a reasonable amount of variation in the shape of your luggage while still keeping a general cap on its size. It’s useful for determining if your carry-on baggage meets the size requirements before you reach the airport check-in or TSA. Knowing the maximum size your personal item or carry-on luggage can be will save you a headache during your travel day.

Although each airline sets its luggage size limits separately, a limit of 62 linear inches for checked bags is practically standard across the industry. So both of the example bags given would be allowed, because their total linear measurement (51 linear inches) is less than the 62-inch limit. However, if your bag were to measure 35 inches high by 16 inches wide by 14 inches deep, its linear dimensions would be 35 + 16 + 14 = 65 linear inches, or just over the typical 62-inch limit.

The exact implications of trying to check a too-large bag vary by airline. In a few cases, oversize bags might be rejected outright, but usually, you'll be allowed to check the bag in exchange for a hefty fee. Size restrictions are different for different classes of tickets, like economy or first class, and even across different airlines like Southwest or American Airlines for example. The one constant is that airlines measure baggage in linear inches like outlined above.

If you don’t want to whip out the tape measure and check if your bag will meet the size limits to successfully fit in the overhead bin, feel assured that most duffel bags, backpacks, laptop bags and purses will not exceed the maximum size of a carry-on bag.

When it comes to carry-on luggage, it is probably better to be safe than sorry and measure that. Soft bags can be squished into the correct size if need be, but hard shell luggage can’t do the same. You may be thinking too, “If I get on the plane and it doesn’t fit, they’ll have to let me keep it there anyway,” but this is false. Flight attendants will force you to check that bag if it does not fit, even if you’ve already made it onto the plane. Avoid the hassle and make your air travel easier by just double-checking the size in advance.

When measuring hard shell luggage, verify that your suitcase is a "box" with six flat surfaces that meet at right angles. When a suitcase has rounded corners, measure to where the corners would be if they were not rounded. Some suitcases will have handles that stick out even after you have pushed them in as far as they will go. With those suitcases, measure the object as if it was a box without protrusions.