When does a padded envelope count as a package instead of a large envelope?
A padded envelope mails at First-Class Mail large envelope prices only if it is no more than 15 x 12 in. and 3/4 in. thick, flexible, rectangular and evenly thick (no bump over 1/4 in.), and weighs 13 oz or less.
If it is rigid, lumpy, holds a box, or is thicker than 3/4 in., it is a parcel and pays Ground Advantage prices: a 6 oz piece goes from $3.14 with stamps to $8.80 at the counter or $7.86 online to Zone 4.
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
“Not more than 15 inches long, or more than 12 inches high, or more than 3/4 inch thick.”
“Boxes—with or without hinges, gaps, or breaks that allow the piece to bend—are not flats. Tight envelopes or wrappers that are filled with one or more boxes are not flats.”
“Flat-size mailpieces must be uniformly thick so that any bumps, protrusions, or other irregularities do not cause more than 1/4-inch variance in thickness.”
“The piece is not flexible if it cannot bend at least 1 inch vertically without being damaged.”
“Flat-size mailpieces that do not meet the eligibility standards in 2.3 through 2.4 are considered parcels and must pay the applicable parcel prices.”
“Large envelope-sized pieces that are rigid, nonrectangular, or not uniformly thick pay parcel prices.”
“When a postal employee observes a customer demonstrating that a flat-size piece is flexible according to these standards, the employee should not perform the test.”
What it costs, with examples
| Piece | Counts as | Price |
|---|---|---|
| Paperback, 6 oz, in a 9 x 12 in. padded mailer, 1/2 in. thick, bends easily | large envelope | $3.14 with stamps (no tracking) |
| The same book in a mailer 1 in. thick | parcel (over 3/4 in.) | $8.80 at the counter, $7.86 online |
| DVD in its case, 5 oz, in a padded mailer | parcel (a hinged case is a box) | $8.80 at the counter, $7.86 online |
| Shirt, 12 oz, in a 10 x 13 in. poly mailer, 2 in. thick | parcel | $7.86 online by weight, or $8.74 at the Cubic soft-pack price |
| Paperback, 14 oz, in a thin padded mailer | parcel (First-Class Mail stops at 13 oz) | $11.10 at the counter, $7.86 online, or $4.39 by Media Mail |
| Weight | Large envelope (stamps) | Ground Advantage online | Ground Advantage at the counter |
|---|---|---|---|
| 1 oz | $1.69 | $7.86 | $8.80 |
| 4 oz | $2.56 | $7.86 | $8.80 |
| 8 oz | $3.72 | $7.86 | $8.80 |
| 13 oz | $5.24 | $7.86 | $11.10 |
| 14 oz | not allowed (over 13 oz) | $7.86 | $11.10 |
Edge cases
- Rigid insert: a piece that bends 1 in. but has something stiff inside must pass a second test: a flat 10 in. or longer is pushed 5 in. off the table and both ends must bend 2 in.; a shorter one goes half its length off and both ends must bend 1 in. (DMM 201.4.3).
- Loose contents: nonpaper contents must not shift more than 2 in. inside a flat if that would make it uneven or burst it (DMM 101.2.4).
- No tracking: USPS says most of its services include USPS Tracking "except First-Class Mail service" (USPS), so a large envelope has none.
- 13 oz cap: First-Class Mail letters and flats can't weigh more than 13 oz (DMM 101.6.1).
- Envelope strength: over 1 lb or over 1 in. thick, USPS wants a sturdier envelope: 28-lb paper or extra-strength material with a Mullen rating over 90 psi (DMM 601.4.1).
- Books and media: a book in a padded mailer can go Media Mail at $4.39 up to 1 lb, flat or parcel (Media Mail rates).
- Edges don't count: when USPS checks the 1/4 in. variance, it leaves out the outer 1 in. of each edge if the contents don't reach into it (DMM 101.2.4).
- Too small to be a flat: a mailer no larger than 11-1/2 x 6-1/8 in. and 1/4 in. thick is letter-size, not a flat (DMM 101.1.1, 101.2.1). Up to 3.5 oz it pays letter prices (over 3.5 oz, large envelope prices), plus the 49¢ surcharge if it is rigid or lumpy, or if its outside isn't paper, as with a poly bubble mailer (DMM 101.1.2; nonmachinable surcharge).
- Square corners: a flat must be rectangular, with square corners or rounded corners of no more than 1/8 in. radius (DMM 101.2.1).
- At the counter: if the clerk watches you show that the piece passes the bend test, the clerk does not need to run it (DMM 101.2.3); for commercial mail DMM 201.4.3 says the employee should not perform it (DMM 201.4.3).
What to do
- Bend-test it yourself: hold it halfway off a table edge and press 1 in. from the end. If it won't bend 1 in. without damage, price it as a parcel.
- Keep it at 3/4 in. thick or less and the contents flat and secured.
- For anything rigid or that needs tracking, buy a Ground Advantage label online: $7.86 to Zone 4 for up to 15.999 oz.
Questions
Can a bubble mailer go as a large envelope?
Yes, if it passes all the flat tests: up to 15 x 12 in., 3/4 in. thick, flexible, evenly thick within 1/4 in. and 13 oz or less (DMM 101.2).
Is a 1 inch thick envelope a package?
Yes. Over 3/4 in. thick it is not a flat, so it pays parcel prices (DMM 101.6.4).
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
- USPS: Mail and Shipping Services
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