Which packages qualify for USPS Cubic pricing?
Ground Advantage Cubic takes parcels up to 1 cubic foot, 20 lb and 22 inches on the longest side; Priority Mail Cubic takes up to 0.5 cubic foot with the same 20 lb and 22 in. limits. Rolls and tubes don't qualify.
Cubic is a commercial price, available through PC Postage label services that offer it, not at the Post Office counter. Boxes are tiered by volume with each side rounded down to the 1/4 inch; poly mailers and padded envelopes by length plus width, up to 36 in.
Rates verified on
Postage in the examples is from Notice 123 effective Oct 4, 2026, which includes USPS's temporary holiday prices for Ground Advantage and Priority Mail until 12 a.m. CT Jan 17, 2027. The fees quoted here are the same as in the July 12, 2026 edition, before the holiday prices began.
The rule, in USPS's words
“Each cubic mailpiece, including soft packs and padded envelopes under 1.3.4, must measure 1 cubic foot or less, weigh 20 pounds or less, and the longest dimension must not exceed 22 inches.”
“Each cubic mailpiece, including soft packs and padded envelopes under 1.3.4 must measure .50 cubic foot or less, weigh 20 pounds or less, and the longest dimension must not exceed 22 inches.”
“Round down (see 604.7.0) each measurement to the nearest 1/4 inch.”
“Cubic-tier measurements for soft pack (poly, plastic, cloth, or similar soft packaging) and padded envelopes are based, in inches, on the outside dimensions of length plus width of the original packaging material.”
“The maximum total of length plus width must not exceed 36 inches.”
What it costs, with examples
| Box (inches), weight | Cubic feet | Tier | Cubic price | Price by weight |
|---|---|---|---|---|
| 9 x 6 x 4, 4 lb (a stack of paperbacks) | 0.125 | 0.20 | $9.92 | $13.89 |
| 6-1/8 x 5-7/8 x 6-3/8 (USPS's own example), 2 lb | 0.125 | 0.20 | $9.92 | $10.50 |
| 12 x 12 x 12, 15 lb | 1 | 1.00 | $18.68 | $22.90 |
| Mailer (inches) | Length + width | Tier | Ground Advantage Cubic | Priority Mail Cubic |
|---|---|---|---|---|
| 10 x 13 | 23 | 0.20 | $9.92 | $14.02 |
| 12 x 15-1/2 | 27.5 | 0.30 | $11.51 | $17.41 |
| 14-1/2 x 19 | 33.5 | 0.40 | $13.48 | $21.98 |
| 19 x 24 | 43 | not eligible (over 36 in.) | pays by weight | pays by weight |
Edge cases
- Folding doesn't lower the tier: a soft pack is measured by the outside size of the original mailer, not the folded-over size.
- Expandable mailers (pleated) are measured like boxes, by length x width x height (DMM 283.1.3.4).
- Rounding goes down for cubic but up for dimensional weight: 6-1/8 in. counts as 6 in. for the cubic tier and as 7 in. for dimensional weight.
- Fees still apply: Notice 123 lists the $4.50 characteristics fee and the HAZMAT fees under both cubic price tables.
- Over a limit (more than 20 lb, 22 in. or 1 cubic foot), the parcel pays by weight, and by dimensional weight over 1 cubic foot.
- Since July 12, 2026: the longest side allowed rose from 18 to 22 in. and soft packs moved to five tiers (tracker entry).
- Packing clothes and other soft goods: soft goods from 5 to 20 lb must be packed in material with at least a 70-lb outer-ply basis weight, boxes of soft goods up to 5 lb must be filled to capacity, and shrinkwrap alone isn't acceptable (DMM 601.3.9).
What to do
- For small, heavy items (books, tools, media), price the smallest box at cubic before paying by weight: the 9 x 6 x 4 in. example saves $3.97 to Zone 5.
- Pick the smallest mailer the item fits; an inch less in length plus width can drop a tier.
- Use a label service that offers cubic prices; the counter doesn't sell them.
Questions
Can I get USPS cubic pricing at the Post Office?
No. Cubic prices are commercial prices for PC Postage and permit customers (DMM 283.1.2, 1.3; DMM 223.1.3).
What is the weight limit for USPS cubic?
20 lb for both Ground Advantage Cubic and Priority Mail Cubic (DMM 283.1.3.1, DMM 223.1.3.1).
Sources
Rates verified on from each official page below.
Free 1-page Reseller Cheat Sheet: fees on 8 platforms, Media Mail and stamp prices
What each platform takes from a $10, $25 and $50 sale, Media Mail 1-10 lb, Ground Advantage to Zones 1, 5 and 8, and the Forever stamp, on one printable page. The link appears as soon as you sign up.