Shipping Glossary

USPS Cubic Pricing

What cubic pricing is, who qualifies, and how it can save you money on heavy, small packages.

Definition

Cubic pricing is a USPS rate structure available through commercial pricing that charges based on a package's volume (cubic size) rather than its weight. It is available for Priority Mail packages that measure 0.5 cubic feet or less, with no weight limit up to 70 lbs.

What Is Cubic Pricing?

USPS cubic pricing divides packages into five tiers (0.1 to 0.5 cubic feet) based on their dimensions. Because there is no weight limit within these tiers, cubic pricing is especially valuable for small but heavy items like candles, books, weights, or liquids. The rate is determined solely by the cubic tier and the shipping zone. Cubic pricing is only available through USPS commercial pricing platforms and shipping software -- you cannot get cubic rates at the post office counter. Shippers using platforms like I'd Ship That automatically receive cubic pricing when it offers the lowest rate.

Formula

Cubic size = (L x W x H) / 1,728. If the result is 0.50 or less, the package qualifies for cubic pricing. Tiers: 0.1, 0.2, 0.3, 0.4, 0.5 cubic feet.

Example

A 10 x 8 x 6 inch box containing a 15 lb candle has a cubic size of 0.28 cubic feet, placing it in tier 0.3. Instead of paying the 15 lb Priority Mail rate (which could be $20+), you might pay $9-$12 depending on the zone.

Why It Matters

Cubic pricing can save 20-40% on shipping costs for small, heavy items compared to weight-based pricing. If you ship products that are dense and compact, cubic pricing is one of the biggest cost-saving opportunities available.

How Each Carrier Handles Cubic Pricing

USPS

USPS offers cubic pricing exclusively for Priority Mail through commercial pricing. Packages must be 0.5 cubic feet or less with no weight limit up to 70 lbs. Five pricing tiers are based on cubic volume, and rates vary by zone.

FedEx

FedEx does not offer a cubic pricing equivalent. All FedEx shipments use weight-based or DIM weight pricing, whichever is greater.

UPS

UPS does not offer a cubic pricing equivalent. All UPS shipments use weight-based or DIM weight pricing, whichever is greater.

Tips

Cubic pricing is ideal for dense items like candles, soaps, books, and small electronics

Always measure your package dimensions carefully -- even a fraction of an inch can bump you into a higher cubic tier

Use I'd Ship That to automatically detect when cubic pricing beats standard Priority Mail rates

Cubic pricing is only available through commercial shipping platforms, not at the post office

Related Terms

DIM Weight • Flat Rate Shipping • Commercial Plus Pricing

Frequently Asked Questions

Who qualifies for USPS cubic pricing?

Cubic pricing is available to shippers using USPS commercial pricing through approved shipping platforms and software. You cannot access cubic rates at a post office counter or through Click-N-Ship. The package must also be 0.5 cubic feet or less.

Is there a weight limit for cubic pricing?

No. That's the main advantage of cubic pricing. As long as your package is 0.5 cubic feet or less and under the USPS 70 lb maximum, the rate is based entirely on volume and zone, regardless of how much it weighs.

How do I calculate my cubic tier?

Multiply length x width x height in inches, then divide by 1,728 to get cubic feet. If the result is 0.50 or less, your package qualifies. The five tiers are 0.1, 0.2, 0.3, 0.4, and 0.5 cubic feet.

Is cubic pricing cheaper than flat rate?

For small, heavy items shipping shorter distances (zones 1-4), cubic pricing is almost always cheaper than flat rate. For longer distances or lighter items, flat rate may be more economical. Comparing both options for each shipment is the best approach.

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