Get USPS Priority Mail Cubic® pricing with no markup or fees

Other shipping software adds tons of markup on top of the actual cubic pricing. Pirate Ship passes through Priority Mail Cubic rates at Commercial Pricing® (the deepest discounts available from USPS) with no markup, per-label costs, or monthly fees.

Priority Mail Cubic (or "Cubic" as it's commonly called) is a secret sub-service of Priority Mail® that’s usually only offered to businesses who ship at least 50,000 packages per year. But with Pirate Ship you can access the same rates with no minimum volume requirements.

The pricing for Priority Mail Cubic is based on the outer dimensions of your package, rather than the weight. There are 5 different tiers of pricing that your package could be in depending upon its size, and any box that's under half of a cubic foot in volume can qualify, as long as none of the dimensions go over the 18" maximum. You can ship up to 20 pounds for no extra cost, making it the cheapest shipping service available for small boxes.

To calculate which Cubic pricing tier your package is in:

1. Measure the outer length, width, and height of your package (18" max in any dimension). If any of the measurements are over the nearest quarter inch, round down to the nearest quarter inch (for example, 5.6" inches turn into 5.5" inches);
2. Multiply the Length x Width x Height, then divide the result by 1728;
3. The resulting number is the size of the package in cubic feet, and you can use the Priority Mail Cubic® rate chart above to determine the pricing. Round up fractional results to the next tier (so for example, a package that is 0.24 cubic feet will be in the 0.3 tier).

Note that Priority Mail Cubic packages cannot be larger than 0.5, half of a cubic foot, but larger packages can be sent with weight-based Priority Mail.

You can also ship soft pack poly or padded envelopes with Priority Mail Cubic Softpack. Cubic Softpack pricing is the same as if you were shipping a box, but the formula for calculating the pricing tier is different.

To calculate which pricing tier a softpack envelope is in:

1. Measure the Length and Width of the empty envelope or softpack mailer (in inches);
2. If the measurements exceed the nearest quarter inch, round down to the nearest 1/4" inch (for example, 9.9" inches turns into 9.75" inches);
3. Add the measurements together and determine which pricing tier your envelope is in:
   
   Cubic Softpack Tier 0.1 - Length plus Width measures more than 0" up to 21"
   Cubic Softpack Tier 0.2 - Length plus Width measures more than 21" up to 27"
   Cubic Softpack Tier 0.3 - Length plus Width measures more than 27" up to 31"
   Cubic Softpack Tier 0.4 - Length plus Width measures more than 31" up to 34"
   Cubic Softpack Tier 0.5 - Length plus Width measures more than 34" up to 36"

Note that neither dimension can be over 18", and the total size for Priority Mail Cubic Softpack cannot exceed 36". Larger envelopes can be sent via weight-based Priority Mail.