Nothing matches the sadness – and financial hurt – of hauling your carefully packed bag up to the airline luggage counter, only to see it slapped with an "oversize" label and the according fees, which, depending on your airline, can run into the triple digits. 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.

Understanding Linear Inches

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.

Checked Bag Size Limits

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.

Tip

Worried about somebody getting into your checked bag while you're separated? Consider securing it with a TSA-approved lock.

Carry-On Size Limits

Most airlines give very specific limits on height, width and depth for carry-on bags. But in some cases, they'll also give the sizing portion of their carry-on regulations in linear inches. Like the rules for checked bags, these vary from airline to airline, but a maximum limit of 45 inches is quite common.

The Consequences of Oversize Bags

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. Said fees vary by airline and can easily run into the triple digits, so always check your airline's fee structure before you head to the ticket counter. You may just find that you don't really need everything you've packed.