Some carriers charge a special rate for packages that are large but relatively light. This is known as a balloon-rate. 

For example, prior to Jan 27, 2019 USPS had charged a balloon-rate of 20 lb rate postage for Priority Mail and Parcel Select shipments that meet the following characteristics:

  • The shipment weighs less than 20 lbs
  • The shipment is travelling to a destination within USPS Zones 1 - 4
  • The shipment has dimensions such that the sum of the length* & girth exceed 84 inches but are less than 108 inches 

Please note that while balloon-rates appear similar to dimensional weight charges, shipments are typically charged one or the other. 

*Length is the measure of the longest side. Girth is the measure of the thickest area perpendicular to the length. This measurement may also be calculated as below:

Length + (2* Height) + (2* Width)

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