The most significant change made last May to Priority Mail service was the introduction of “dimensional-weight” pricing. Dimensional-weight pricing is based on the cubic capacity (size) of a parcel rather than on its weight alone. This holiday mailing season, many customers may mail packages for the first time this year, so the changes may be new to them.
Dimensional-weight pricing converts the cubic size (capacity) of an item into a weight. If a large parcel is relatively light but addressed for delivery to Zones 5–8, it could be charged as a heavier-weight piece, based on a standard issued by the International Air Transport Association (IATA). This standard is well known in the U.S. shipping industry, and a similar standard is used by other carriers to determine the prices for parcels shipped by air. Dimensional-weight pricing applies only to Priority Mail items larger than 1 cubic foot (1,728 cubic inches) traveling to Zones 5–8, where air transportation is generally used. It does not apply to Priority Mail International™ items.
Another change was the Priority Mail “balloon rate.” The 20-pound minimum balloon rate applies to parcels measuring larger than 84 inches in combined length and girth and weighing less than 20 pounds. While dimensional-weight pricing applies to Zones 5–8, balloon-rate pricing applies only to Priority Mail parcels locally and to Zones 1–4. This limits the balloon rate to those items for which ground rather than air transportation is generally used.
To determine if a Priority Mail item is subject to either of the two, follow the easy steps in the following sections.
First, weigh the item. As always, any fraction of a pound is rounded up to the next whole pound. For example, if the item weighs 5.2 pounds, the weight increment is 6 pounds.
Next, determine the zone to which the parcel is addressed. If the item is sent to a local address or to Zones 1–4 and does not exceed 84 inches in combined length and girth, postage will be based on the actual or “scale weight” and the appropriate zone. If the combined length and girth exceeds 84 inches, postage will be based on the item’s scale weight or 20 pounds, whichever is greater, and the appropriate zone.
If the item is being sent to an address in Zones 5–8, balloon rates do not apply, but dimensional-weight pricing may apply.
First, weigh the item. For rectangular (boxlike) items, measure the length (longest dimension), width, and height. (Note: If no dimension is more than 12 inches, the dimensional-weight price will not apply.) Round-off each individual measurement to the nearest whole inch (e.g., 10–3/8 inches is considered 10 inches; 12-1/2 inches is considered 13 inches).
Next, multiply the length by the width by the height. The result is the cubic capacity (expressed in cubic inches). If the result is 1,728 cubic inches or less, dimensional-weight pricing does not apply because the parcel does not exceed 1 cubic foot capacity. Postage is based on the actual weight and the appropriate zone. If the result exceeds 1,728 cubic inches, divide it by 194 (the “dim factor”) to determine the dimensional weight. Round up any fraction of a pound to the next whole pound. The applicable postage is based on the scale weight or the dimensional weight, whichever is greater, and the appropriate zone.
If a parcel is not rectangular (boxlike), it is considered to be “irregularly shaped.” Such items occupy space (and displace other items) in transportation containers differently than boxlike parcels. In consideration of this, an “adjustment factor” of 0.785 is used when calculating the dim weight, ultimately lowering the assessed rate of postage. The Postal Service™ is the only shipping company to make such an adjustment. The adjustment factor is simply plugged into the dimensional-weight formula. Just as with regular boxlike parcels, measure the item’s longest dimension (length), width, and height. However, the width and height are not likely to be uniform dimensions and will need to be measured at their maximum cross-sections. For example, in measuring the width and height of a football, the maximum cross-section is in the middle, where the football is thickest. The length is the straight-line distance from one tip to the other. Multiply the length by the width by the height, and then multiply by the 0.785 adjustment factor. If the result is 1,728 cubic inches or less, dim-weight pricing cannot apply because the parcel does not exceed 1 cubic foot. Postage will be based on the scale weight and the appropriate zone. If the result exceeds 1,728 cubic inches, divide it by 194 (the same dim factor) to determine the dimensional weight. Again, any fraction of a pound is rounded up to the next whole pound.
If the resulting dimensional weight is greater than 70 pounds, the package is charged the applicable 70–pound rate.
