Priority Mail Cubic
Delivered in 1 to 3 business days
If your package is around the size of a shoebox or smaller, it's perfect for this secret dimension-rated service that lets you ship up to 20 pounds for no additional cost.
Max Any Dimension: 18" inches
Max Cubic Volume: 0.50 cubic ft
Max Weight: 20 pounds
Cheapest pricing for small packages
Priority Mail Cubic is the best way to ship small packages with the Postal Service that weigh between 1 and 20 pounds.
Delivered in 1 to 3 business days
USPS will deliver Priority Mail Cubic packages to anywhere in the USA (including Alaska, Hawaii, Puerto Rico, and territories) within 1 to 3 days.
Free package tracking included
All Priority Mail Cubic packages included full door-to-door tracking, so you can keep an eye on your shipments.
$100 insurance included for free
Priority Mail Cubic postage purchased from Pirate Ship includes $100 of USPS liability insurance for free.
Cubic is the best shipping service
Businesses that optimize their packaging for USPS Cubic pricing unlock huge savings and efficiencies.
Save up to 89% by using Pirate Ship
Priority Mail Cubic pricing isn't available at the Post Office and it'll save you up to 89% off standard retail prices.
Calculate your Priority Mail Cubic pricing tier
Get rates BELOW Commercial Pricing for Priority Mail Cubic
Pirate Ship offers Priority Mail Cubic rates BELOW Commercial Pricing® (the deepest discounts publicly available from USPS) for shipments to and from the lower 48 states, with no markup, per-label costs, or monthly fees.
Only for shipments to/from the lower 48 states. Create a free account & get a rate quote to see the rates.
Priority Mail Cubic is one of the best kept secrets for shipping packages that weigh up to 20 lbs
Priority Mail Cubic (or "Cubic" as it's commonly called) is a secret sub-service of Priority Mail® that shippers of small but relatively heavy packages use to optimize their shipping. With Pirate Ship you can access even deeper discounts than Commercial Pricing for Priority Mail Cubic 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 one of the cheapest shipping services available for small boxes.
To calculate which Cubic pricing tier your package is in:
- 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);
- Multiply the Length x Width x Height, then divide the result by 1728;
- 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.
Get the cheapest Priority Mail Cubic Softpack pricing
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:
- Measure the Length and Width of the empty envelope or softpack mailer (in inches);
- 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);
- 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.