USPS Cubic Pricing: Save 30-60% on Heavy Packages

USPS Cubic pricing is a special rate structure that charges based on package volume (cubic size) rather than weight, for packages up to 20 lbs.

The cubic size is calculated as (LxWxH)/1728, resulting in cubic feet. Packages are sorted into tiers: 0.1 (up to 0.1 cu ft), 0.2 (up to 0.2 cu ft), 0.3 (up to 0.3 cu ft), 0.4 (up to 0.4 cu ft), and 0.5 (up to 0.5 cu ft).

Each tier has a flat rate per zone, regardless of weight up to 20 lbs. This makes Cubic pricing incredibly valuable for dense, heavy items.

Calculate cubic size: (Length x Width x Height) / 1728 = cubic feet

Examples:

6x6x6 box = 216/1728 = 0.125 cubic feet (Tier 0.2)

5x5x4 box = 100/1728 = 0.058 cubic feet (Tier 0.1)

10x8x5 box = 400/1728 = 0.23 cubic feet (Tier 0.3)

12x10x6 box = 720/1728 = 0.42 cubic feet (Tier 0.5)

Lower tiers have lower rates, so using the smallest box possible maximizes savings.

Cubic pricing excels for:

- Supplements and vitamins (heavy bottles, small boxes)

- Books and media (dense, compact)

- Hardware and tools (metal parts in small packaging)

- Cosmetics and beauty products (heavy glass containers)

- Specialty foods (jars, cans, dense items)

These items often weigh 5-20 lbs but fit in compact boxes. Without Cubic, weight-based rates would be $15-30. With Cubic, they're $8-15.