Cubic Pricing, SoftPack

Cubic pricing is a USPS program that allows packages up to a certain weight limit to be billed as flat-rate boxes by dimension. You can use your own box. To determine if your box qualifies, use the following calculation:

  1. Measure the length, width, and height of your box in inches. Round down to the nearest 1/4 (or 0.25) inch.
  2. Multiply the length by the width by the height and then divide that number b 1,728.

If the value comes out to less than 0.50, your package qualifies for one of the five cubic tier rates. If your value is in between two of the rate tiers, it belongs to the higher rate tier.

For example, if you have a package that measures 11in. in length, 9in. in width, and 5.75in. in height, the cubic ft. value would come out to 569.25/1,728 = 0.329. This is over 0.30 so the package qualifies for the cubic rate tier 0.40.

Teapplix provides USPS support for cubic pricing. Simply select "Priority Mail" as the shipping method and specify dimensions and weight. Teapplix will automatically provide the cubic discount if the resulting price is cheaper than normal weight and zone-based pricing.


Softpack is a form of cubic pricing for large Flat Envelopes or Parcels. This is supported by Teapplix USPS. Softpack is a manual select. You must select the Priority Mail Softpack shipping method. This method is always present when you have USPS turned on.

  • In Teapplix USPS, if you select Priority Mail Softpack, you still need to enter all three dimensions and can use 1" or 2" as the depth dimension. If the dimension is missing, we will use the weight-based shipping rate. If the dimension exceeds 18 x 18 x 2 you will get an error. Otherwise, you will get softpack pricing. (Please note: softpack pricing may be lower or higher than normal priority mail. It is because the rate is only based on two of the long dimensions. So this is not auto rate shopped with Teapplix USPS.  To add rate shop, you should use Teapplix Rate Shop methods instead)