Does USPS round up package weight?
Yes. Ground Advantage is priced in steps of 4, 8, 12 and 15.999 oz and then by the pound, and any fraction rounds up to the next step: 4.1 oz pays the 8 oz price and 1.25 lb pays the 2 lb price. Priority Mail rounds any fraction up to the next whole pound, with 1 lb as the minimum.
The last ounce step is 15.999 oz because 16 oz is the 1 lb row: a package of exactly 1 lb pays the 1 lb price, $9.29 online to Zone 5 against $8.24 for 15.999 oz.
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
“Any fraction of an ounce over the 4-ounce, 8-ounce, 12-ounce, and 15.999-ounce increments is rounded to the next price increment.”
“Any fraction of a pound is considered a whole pound. For example, if an item weighs 1.25 pounds, the weight (price) increment is 2 pounds.”
“The minimum postage amount per addressed piece is the 1-pound price.”
“if you’re sending a Priority Mail package that weighs 5 lbs 2 oz, you would round up to the pound and pay the 6 lb-rate.”
“Include the weight of everything, including packing materials.”
What it costs, with examples
| Package weighs | Pays the price for | Post Office | Online |
|---|---|---|---|
| 3.9 oz | 4 oz | $9.35 | $8.24 |
| 4.1 oz | 8 oz | $9.35 | $8.24 |
| 8.1 oz | 12 oz | $11.70 | $8.24 |
| 12.1 oz | 15.999 oz | $11.70 | $8.24 |
| 16 oz (1 lb exactly) | 1 lb | $11.70 | $9.29 |
| 1 lb 0.1 oz | 2 lb | $14.85 | $10.50 |
| 2 lb 1 oz | 3 lb | $15.70 | $12.12 |
Edge cases
- Equal steps at the counter: at retail prices, 4 oz and 8 oz cost the same ($9.35 to Zone 5), and so do 12 oz, 15.999 oz and 1 lb ($11.70).
- One price under 1 lb online: commercial Ground Advantage charges the same for every weight up to 15.999 oz ($8.24 to Zone 5): since July 12, 2026, USPS has set the same commercial price for every ounce step within a zone. The Governors said ending the ounce-based differences raised commercial Ground Advantage prices 11.8 percent on average (Governors' Decision 26-2; tracker entry).
- Priority Mail under 8 oz online: Notice 123 has a 0.5 lb commercial Priority Mail row, at the same price as 1 lb ($13.82 to Zone 5).
- Dimensional weight replaces the rounded weight for boxes over 1 cubic foot when it is higher (dimensional weight).
- Media Mail rounds up by the pound with a 1 lb minimum (Media Mail rates).
What to do
- Weigh the sealed package with all packing, then trim packing if you are just over a step: getting an 8.2 oz package under 8 oz saves $2.35 at the counter to Zone 5.
- Just over a pound costs the 2 lb price: $1.21 more online to Zone 5 than 1 lb.
- Price every weight and zone on USPS shipping cost by weight.
Questions
What does 15.999 oz mean on USPS prices?
It is the last ounce step for Ground Advantage, just under 1 lb. Anything over 12 oz up to 15.999 oz pays that price; a package of 16 oz or more pays by the pound (DMM 133.1.2).
Does USPS round 1.1 lb up to 2 lb?
Yes, for Ground Advantage and Priority Mail: any fraction of a pound counts as a whole pound (DMM 133.1.2, DMM 123.1.1).
Sources
Rates verified on from each official page below.
- USPS Notice 123, Price List (effective Oct 4, 2026)
- USPS Domestic Mail Manual 123: Priority Mail retail prices and eligibility
- USPS Domestic Mail Manual 133: First-Class Mail and Ground Advantage retail prices and eligibility
- USPS Domestic Mail Manual 283: Ground Advantage commercial prices and eligibility
- USPS: How to Send a Package (domestic)
- USPS Governors' Decision 26-2 (Federal Register, May 14, 2026): July 12, 2026 competitive price and classification changes
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.