Can you tape two boxes together and ship them as one USPS package?
Yes, if the packages are about the same size or shape, securely wrapped or fastened together, and together stay within the weight and size limits. It doesn't work with USPS Flat Rate Envelopes or Boxes.
The joined parcel is measured as one box, so it can tip into dimensional weight or a length fee. Two 2 lb boxes to Zone 4 cost $17.82 on two Ground Advantage labels and $11.30 taped together on one.
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
“With the exception of USPS-produced Flat Rate Envelopes and Boxes, two or more packages may be mailed as a single parcel”
“if they are about the same size or shape, if they are securely wrapped or fastened together, and if they do not together exceed the weight or size limits.”
“Twine or cord should not be used for closure and reinforcement, as it could interfere in mail processing equipment.”
“When banding is used for closure and reinforcement, it must encircle the length and girth of the package at least once.”
What it costs, with examples
| How you ship | Zone 4 | Zone 8 |
|---|---|---|
| Two labels, one per box | $17.82 | $26.84 |
| Taped side by side, 16 x 10 x 6 (960 cubic in.), 4 lb | $11.30 | $19.06 |
| Saved by taping | $6.52 | $7.78 |
| Three taped end to end, 30 x 8 x 6, 6 lb | $16.70 (with the $4.50 length fee) | $26.23 |
| Three stacked, 10 x 8 x 18 (1,440 cubic in.), 6 lb | $12.20 | $21.73 |
Edge cases
- The joined size counts: over 1,728 cubic inches it is billed at dimensional weight, and a longest side over 22 in. adds $4.50 (length fee).
- Flat Rate boxes can't be joined; each Flat Rate box is its own piece.
- About the same size or shape: the rule doesn't cover a small box strapped to a big one.
- Weight: the total must stay at 70 lb or less (size and weight limits).
- Tape, not string: use packing tape at least 2 in. wide (DMM 601.3.14); twine or cord can catch in machines.
What to do
- Stack or line up the boxes so the longest side stays at 22 in. or less, then tape all seams and wrap tape around both boxes.
- Price the joined box with its real dimensions before you tape it; in the table, three boxes end to end cost $4.50 more than the same three stacked, because the line is 30 in. long.
- Put one label on the joined parcel and cover any old labels on the inner boxes (reusing boxes).
Questions
Can I tape two Priority Mail Flat Rate boxes together?
No. USPS-produced Flat Rate Envelopes and Boxes are the one exception to the rule allowing packages to be joined (DMM 101.3.3).
Is it cheaper to ship two boxes as one?
Usually, because one 4 lb label costs less than two 2 lb labels: $6.52 less to Zone 4 by Ground Advantage online. The saving shrinks if the joined box goes over 22 in. long (a length fee) or over 1 cubic foot (dimensional weight).
Sources
Rates verified on from each official page below.
- USPS Notice 123, Price List (effective Oct 4, 2026)
- USPS Domestic Mail Manual 101: physical standards for retail letters, flats and parcels
- USPS Domestic Mail Manual 201: physical standards for commercial mail (flats, parcels, nonstandard parcels)
- USPS Domestic Mail Manual 601: mailability, packaging and USPS-produced packaging
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.