Weight-based Priority Mail applies when packages are too big for Priority Mail Cubic
Weight-based Priority Mail: Regular Priority Mail is one of the best ways (although not always the cheapest way) to ship packages that are too big for Priority Mail Cubic.
Priority Mail Packaging: You don't have to use USPS-branded boxes for weight-based Priority Mail, but you can use any of the "Mailing Boxes" that USPS provides.
See a list of those USPS boxes here.
Sometimes Cheaper than Cubic Rates: In some cases, weight-based Priority Mail rates will be cheaper than dimension-based Priority Mail Cubic rates.
In those cases, Pirate Ship gives you whichever one is cheaper, which is why it’s important to always be accurate with weights and dimensions 😉
You can see the differences in the rate comparison table on this page.
Watch out for Dimensional Weight pricing (DIM Weight)
Dimensional Weight Pricing: If your package is large but lightweight, it could get charged based on the dimensional weight instead of the actual weight.
Dimensional weight charges apply if your package is larger than 1 cubic foot (for example, if the dimensions are 13x13x13") and being shipped to zones 5-9.
Pirate Ship automatically calculates the dimensional weight of your packages. If you'd like to determine the “dimensional weight" yourself, multiply (Length x Width x Height) and divide that figure by the USPS volumetric divisor, 166. If the result is higher than the actual weight of your package, the dimensional weight is what will be charged for.