usps ground advantage box size limit is a consideration for those looking to ship with USPS’s Ground Advantage service. This service is designed for packages that are larger and heavier than typical First-Class Mail items but do not require expedited shipping. The maximum weight for USPS Ground Advantage is 70 pounds, and the maximum size limit for packages is 108 inches in length and girth combined. It’s important to check the size and weight requirements before shipping to ensure your package qualifies for this service.