What is USPS cubic pricing?

Cubic pricing is a USPS price structure for small, heavy packages. For packages up to 20 lb, the price depends on the package's cubic tier and zone instead of its weight. It's available for Priority Mail and USPS Ground Advantage.

How do I calculate my cubic tier?

Measure the outside of the box, round each side down to the nearest quarter inch, multiply length by width by height, and divide by 1,728. Then round up to the next tenth: 0.21 cubic feet falls in the 0.3 tier.

What's the difference between Priority Mail Cubic and Ground Advantage Cubic?

Both use the same tiers and rules up to 0.5 cubic feet, and Ground Advantage Cubic also covers tiers up to 1 cubic foot. Priority Mail is the faster service, with delivery in one to three business days, compared with two to five for Ground Advantage.

How does cubic pricing work for soft packs and padded envelopes?

USPS adds the outside length and width, each rounded down to the nearest quarter inch. Up to 21 inches is the 0.1 tier, up to 27 inches the 0.2 tier, up to 31 inches the 0.3 tier, up to 34 inches the 0.4 tier, and up to 36 inches the 0.5 tier. Measure the mailer flat, before you pack it.

What changed for cubic pricing in 2026?

On July 12, 2026, USPS raised the longest-side limit from 18 to 22 inches and capped Ground Advantage soft packs at the 0.5 tier. Prices changed on Jan. 18, a temporary price increase started April 26, and a peak-season surcharge applies from Oct. 4, 2026, to Jan. 17, 2027.

Is cubic pricing cheaper than a Flat Rate box?

It depends on the box and the zone. At USPS Commercial prices, a 0.1-tier box costs $9.46 to $16.36 in Zones 1 to 8 with Priority Mail Cubic, while a Small Flat Rate Box costs $12.95 to any zone. Compare both for each shipment.

Do I need a minimum shipping volume to get cubic pricing?

Not with Shippo. Every account gets Priority Mail Cubic and Ground Advantage Cubic from the first label. Postage bought at the Post Office uses retail prices, which don't include cubic pricing.

Are these the prices I'll pay in Shippo?

The calculator shows USPS Commercial prices from Notice 123. Your rate in Shippo may be lower. Enter the package in Shippo to see the exact rate before you buy the label.

USPS cubic pricing calculator

Find your Priority Mail Cubic or Ground Advantage Cubic tier and see the USPS price in every zone. Every Shippo account gets cubic pricing from the first label, with no volume minimum.

Get started Find my tier

Find your cubic tier

Enter the outside measurements of your package. Like USPS, the calculator rounds each side down to the nearest quarter inch, then shows your tier and the price for each service.

Enter your package size to see its cubic tier, which USPS services it qualifies for, and the price in every zone.

How USPS cubic pricing works

With cubic pricing, USPS charges by package size and zone instead of weight. Anything up to 20 lb that fits in the box ships at the same price.

Size sets the price

Multiply length, width and height, divide by 1,728, and round up to the next 0.1 cubic foot. That tier and the zone set the price.

Two services, two size limits

Priority Mail Cubic covers tiers from 0.1 to 0.5 cubic feet. Ground Advantage Cubic goes up to 1 cubic foot.

Soft packs use length plus width

For poly mailers and padded envelopes, USPS adds length and width. Up to 21 inches is the 0.1 tier, and the limit is 36 inches.

Cubic limits at a glance

These rules come from the USPS Domestic Mail Manual (DMM 223.1.3 for Priority Mail and 283.1.3 for Ground Advantage), last updated July 12, 2026.

Up to 20 lb

Heavier packages are priced by weight and zone instead.

22 inches on the longest side

USPS raised the limit from 18 inches on July 12, 2026.

Round down to the quarter inch

Each side is rounded down before you multiply, so 10.2 inches counts as 10.

0.5 or 1 cubic foot

The maximum is 0.5 cubic feet for Priority Mail Cubic and 1 cubic foot for Ground Advantage Cubic.

36 inches for soft packs

Length plus width sets five tiers, at 21, 27, 31, 34 and 36 inches.

No rolls or tubes

Rolls and tubes don't qualify for cubic prices.

Get cubic pricing in Shippo

Every Shippo account gets Priority Mail Cubic and Ground Advantage Cubic from the first label, with no volume minimum.

Applied when you qualify

Enter your box dimensions or pick a saved package. When the package qualifies, your Priority Mail and Ground Advantage rates use cubic pricing.

Soft pack template

Shipping in a poly mailer? Choose the Soft Pack package template so the rate uses length plus width.

Compare before you buy

See cubic rates next to UPS, FedEx and other USPS services for the same package, then print the label.

monthly fee on our free plan

Cubic pricing is included on every Shippo plan. USPS size, weight and packaging rules apply.

Frequently asked questions

Compare cubic rates for your next package

Enter your box size, see Priority Mail Cubic and Ground Advantage Cubic next to other services, and print the label with Shippo.