Southwest Airlines allows two checked bags per passenger, each with a maximum total size of 62 inches and a maximum weight of 50 pounds, as of 2015. Southwest calculates the size of the bags by adding the external length, width and height. Bags that exceed the limits may be allowed by the airline for an additional fee.
Additional bags and checked bags that are larger or heavier than the limits may still go on Southwest flights for a $75 per bag charge, as of 2015. The absolute maximum allowed per the oversized baggage policy is 80 inches for overall dimensions and 100 pounds for weight. Bag heavier than 100 pounds can ship as Air Cargo, as long as the passenger qualifies as a Known Shipper per the TSA guidelines.