USPS Priority Mail Cubic pricing is available for packages:
- Weighing less than 20 pounds
- With a Cubic Feet Value* up to 0.5
- With each side measuring 18 inches or less. Note: if more than one side is close to 18 inches, the package will likely still be too large to qualify.
Here’s the equation to determine a package’s Cubic Feet Value*: Length x Width x Height / 1,728
To get the best bang for your buck, remember that when you measure each side, you can round down to the nearest quarter inch. For example, 4 ⅗ (or 4.6) inches would round down to 4 ½ (or 4.5) inches. However, if one side of your package is longer than 18 inches, then the package does not qualify.
Let’s try out the equation using sample dimensions. For example, if our package measures 8.4 x 5 x 7 inches, we first will round down the numbers to the nearest quarter inch, making our dimensions 8.25 x 5 x 7 inches. Then, we multiply the numbers together, which is 288.75. We divide that number by 1,728 to get our Cubic feet value: 0.1671. Since that’s less than 0.5, it qualifies for USPS Cubic pricing.
We’ve also included charts below to quickly estimate and reference which USPS Cubic pricing tier your package falls under.