Each checked bag can weigh 50 pounds or less and be 62 inches in size (length + width + height). What is considered excess baggage? To check more than two bags, each extra bag will result in an additional charge each way as long as it is no bigger than 62 inches (L+W+H) and weighs 50 lbs. or less.

On Southwest Airlines, a checked box must adhere to the same size and weight restrictions as standard suitcases. The maximum weight is 50 pounds (23 kg), and the maximum size is 62 linear inches (length + width + height). If your box exceeds 62 inches but is under 80 inches, it is considered "oversized" and will incur a fee (typically around $75–$125). Boxes larger than 80 inches or weighing over 100 pounds are generally not accepted as checked baggage and must be shipped via Air Cargo. When packing a box, Southwest requires that it be securely closed and sturdy enough to withstand automated handling systems. It is also recommended to remove any old shipping labels or barcodes to prevent sorting errors. Note that "Specialty" boxes, such as those for bicycles or high-value electronics, may have different specific requirements and might require a signature on a "Limited Liability" release form at the ticket counter.