What is the USPS fee for a box over 2 cubic feet?
$21.00 by Ground Advantage and $35.00 by Priority Mail when the box is more than 3,456 cubic inches (2 cubic feet), on top of postage that is already billed by dimensional weight. A big, light box can cost far more than its weight suggests.
For this fee USPS rounds each side off to the nearest whole inch, while dimensional weight rounds each side up, so one box can be under 2 cubic feet for the fee and still be billed by size. Before Jan 18, 2026 the fee was $18.00 and $30.00.
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
“Parcels that exceed 2 cubic feet (3456 cubic inches), add $21.00.”
“Parcels that exceed 2 cubic feet (3456 cubic inches), add $35.00.”
“Dimensions for rectangular pieces are determined by measuring the length, width, and height in inches, rounding off (see 604.7.0) each measurement to the nearest whole inch and multiplying the length by the width by the height.”
“A piece may be subject to both a length (1.7a, 1.7b) and a cube (1.7c) nonstandard fee, or a characteristics (1.7d) and a cube (1.7c) nonstandard fee.”
“Round off requires increasing by 1 the last digit to be kept if the digit to its right, which is not to be kept, is 5 or greater.”
What it costs, with examples
| Box (inches) | Cubic in. for the fee | Ground Advantage fee | Priority Mail fee | Dimensional weight |
|---|---|---|---|---|
| 16 x 15 x 14.4 | 3,360 | none | none | 26 lb |
| 18 x 16 x 12 | 3,456 | none (exactly 2 cu ft) | none | 25 lb |
| 18 x 16 x 14 | 4,032 | $21.00 | $35.00 | 30 lb |
| 24 x 18 x 12 | 5,184 | $21.00 | $35.00 | 38 lb |
| Box (inches) | Billed weight | Postage | 2 cu ft fee | Total |
|---|---|---|---|---|
| 18 x 16 x 14 | 30 lb | $66.98 | $21.00 | $87.98 |
| 16 x 14 x 12 | 20 lb | $26.68 | none | $26.68 |
Edge cases
- Round shapes: for a nonrectangular parcel USPS multiplies the result by 0.785 before comparing it with 3,456 (DMM 283.1.7).
- Two fees, one box: the cube fee stacks with a length fee or with the $4.50 characteristics fee, but a length fee and a characteristics fee never stack with each other.
- Exempt: Priority Mail Flat Rate packaging, Ground Advantage oversized-price parcels (over 108 in. length plus girth) and Ground Return parcels.
- Cubic-priced parcels can't hit it: cubic pricing stops at 1 cubic foot (cubic rules).
- At the counter too: Notice 123 lists the same $21.00 and $35.00 under retail Ground Advantage and Priority Mail.
- Media Mail: the Media Mail tables in Notice 123 list no cube fee.
What to do
- Use a box of 3,456 cubic inches or less after rounding: 18 x 16 x 12 in. is exactly 2 cubic feet and pays no fee.
- Compress soft goods or split a big order into two smaller boxes, and price the two labels against one big box.
- In the 10 lb example above, the smaller box saves $61.30 on one label.
Questions
Is 2 cubic feet the same as 3,456 cubic inches?
Yes. One cubic foot is 1,728 cubic inches (12 x 12 x 12 in.), and Notice 123 writes the limit as 2 cubic feet (3,456 cubic inches).
Does a box over 2 cubic feet also pay dimensional weight?
Yes. Any Ground Advantage or Priority Mail box over 1 cubic foot is billed at the greater of its actual and dimensional weight, and the 2 cubic feet fee is added on top (how dimensional weight works).
Sources
Rates verified on from each official page below.
- USPS Notice 123, Price List (effective Oct 4, 2026)
- USPS Notice 123 effective Oct 5, 2025 (Postal Explorer archive): fees before Jan 18, 2026
- USPS Domestic Mail Manual 283: Ground Advantage commercial prices and eligibility
- USPS Domestic Mail Manual 604: postage payment, rounding and postage discrepancies
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.