The largest sized shipping box USPS allows is 130 inches in combined length and girth. The maximum weight allowed for shipping boxes and parcels is 70 pounds.
In order to ship a box that is 130 inches in combined length and girth, the box must be mailed either by Standard Post or Parcel Select. All other shipping methods have a maximum limit of 108 inches in combined length and girth. USPS measures length by measuring the longest dimension of the box or parcel. Girth is gauged by measuring around the thickest part of the box or parcel. The combined measurements cannot exceed 130 inches.