Priority Mail Cubic is a type of USPS Priority Mail that's priced based on the dimensions of your package instead of the weight. With this you can save up to 90% off the cost of the label.
You can ship packages that are up to half of a cubic foot in volume with this service (which is 12x12x6 inches, or other combinations that make the same volume) and your packages can weigh up to 20 lbs. Note that to qualify for Cubic rates, the maximum size for any dimension is 18 inches.
Depending on the size of your package, there are 5 pricing tiers it will fall into. It’s a good idea to plan your packaging to fit within the smallest tier possible for your package’s content, because it can drastically lower your costs.
Priority Mail Cubic Pricing Tiers
To calculate which of the 5 tiers your package will be in you can use the manual formula below:
Measure your package’s outer dimensions
If any of the measurements exceed the nearest quarter inch, round down to the nearest quarter inch (for example, 5.6 inches turns into 5.5 inches)
Multiply Length x Width x Height, and divide the result by 1728
For example, to calculate the Cubic tier for a box that is 12.3" x 9.5" x 3":
Round down to 12.25" x 9.5" x 3"
Multiply 12.25" x 9.5" x 3" = 349.125
Divide 349.125 / 1728 = .202
Because this package is just over .2 cubic feet, it would be in the 0.3 cubic feet pricing tier.
If it were a slightly smaller box (such as 12x9.5x3) it would be in the 0.2 pricing tier instead and would cost up to 25% less to ship.
You can use Priority Mail Cubic with an envelope or poly mailer
Note that you can also use a padded envelope or poly softpack, but it changes the formula used to determine your pricing tier.
You cannot use Priority Mail Cubic with tubes
Cubic-priced mailpieces may not be rolls or tubes.
2020 USPS Priority Mail Cubic rates
Once you know which USPS Cubic pricing tier your package is in, you can use the rate chart below to determine what it will cost to ship your package, or use our USPS rates calculator.
Simpl Fulfillment offers true Commercial Pricing for Priority Mail Cubic
Other shipping software adds tons of markup on top of the actual Priority Mail Cubic rates. Pirate Ship is the only shipping software that passes through the deepest discounts available for Priority Mail Cubic for free, with no markup, fees, or minimum volume required.