What size hardside checked bag should I buy?

A 28-inch large case is the most common checked size and suits one to two weeks of travel for most people, while 29-30 inch XL bags add capacity for longer trips or families packing into one bag. Remember that most airlines cap a single checked bag at 62 linear inches and around 50 lbs before overweight fees, so a bigger shell is easy to overpack past those limits.