USPS ServicesHow USPS cubic pricing works
Small, heavy packages can ship far cheaper with cubic pricing. Here's how USPS calculates it.
On this page
Cubic pricing charges by the volume of your package rather than its weight, as long as it's small enough. It's available for Priority Mail and Ground Advantage, and it's one of the best-kept secrets in shipping for dense items.
Eligibility
- No side longer than 18 inches
- Total volume of 0.5 cubic feet or less
- Priority Mail Cubic: up to 20 lb. Ground Advantage Cubic: up to 25 lb.
The calculation
Each dimension is rounded down to the nearest ¼ inch, multiplied together, then divided by 1,728 to get cubic feet. The result places your package into one of five tiers: 0.1, 0.2, 0.3, 0.4 or 0.5 cubic feet. For soft packs (poly mailers), USPS uses length and width only with a separate tier chart.
Example: an 8 × 6 × 4 in box is 192 cubic inches, or 0.11 cubic feet, so it ships in the 0.2 tier regardless of whether it weighs 2 lb or 12 lb.
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