When you're bringing a lot of stuff on an airplane trip, inches and pounds matter. Staying within the size and weight restrictions for your checked luggage as set by the airline will save you lots of cash. If you're traveling with Southwest Airlines, going over your size or weight limit will cost you $50 per bag -- and sometimes even more if the bag is especially overweight or oversized. If you think you're close to the limits, you should measure your suitcase before you leave.

Place your suitcase with its bottom legs on the floor.

Stretch your measuring tape from the top to the bottom of the suitcase to measure its height in inches. Write down the measurement.

Stretch your measuring tape from one side to the other side of the suitcase to measure its length in inches. Write down the measurement.

Stretch your measuring tape between the two sides of the suitcase to measure the suitcase's width, or depth, in inches. Write down the measurement.

Add the three numbers you wrote down. Southwest Airlines' size restriction is a combination of 62 inches for the height, length and width of the suitcase, so if the total is higher than 62 inches, you may have to choose another suitcase, or pay the extra fee.

Tip

Since weight is also a big issue, place the suitcase on a scale before you leave for the airport to ensure it weighs less than 50 pounds. In most cases, anything more than that limit will be subject to Southwest Airlines' overweight charge.