
Postage for parcels addressed for delivery to Zones 1-9 and exceeding 1 cubic foot (1,728 cubic inches) is based on the actual weight or the dimensional weight (as calculated in 1.3.1 or 1.3.2), whichever is greater. 1.3 Dimensional Weight Price for Low-Density Parcels to Zones 1-9

See Notice 123-Price List for applicable Priority Mail retail prices. The minimum postage amount per addressed piece is the 1-pound price. For example, if a piece weighs 1.2 pounds, the weight (postage) increment is 2 pounds.

Designing Letter and Reply Mail (PUB 25).
