Uline and Sealed Air
The two largest brands publish their own charts and hold each size stable across product lines. A #4 from Uline reads 9.5 x 14.5 in on the outside across paper, poly-bubble and kraft-lined variants.
Padded packaging
Padded shipping envelope sizes, #000 through #7
The standard bubble mailer numbering runs from #000 at 4 by 8 in up to #7 at 14.25 by 20 in outside. The chart below matches each size to the item that lands in it, and the note below the table explains where the numbering is not standardised across brands. Sizes cross-checked against Uline product listings and the PackagingSupplies chart, read 2026-08-11.
Nine sizes chartedFit examples givenNon-machinable line named
One numbering, many uses
Match the number to the item and the shape rides comfortably through every sorter.
The standard chart
| Size | Outside dimensions (in) | Typical fit |
|---|---|---|
| #000 | 4 x 8 | Small ring or pendant box, USB stick, guitar picks |
| #00 | 5 x 10 | Earrings in a small box, a slim phone case, small paperback |
| #0 | 6 x 10 | Mass-market paperback, small collectibles boxed |
| #1 | 7.25 x 12 | DVD case, small hardcover, boxed cosmetics |
| #2 | 8.5 x 12 | Trade paperback, small tools, folded t-shirt bagged |
| #3 | 8.5 x 14.5 | Longer trade paperback, small hardcover, catalog |
| #4 | 9.5 x 14.5 | Standard hardcover, textbook, brochures |
| #5 | 10.5 x 16 | Larger hardcover, boxed accessories, folded shirt for retail |
| #6 | 12.5 x 19 | Small laptop sleeve, tablet, boxed footwear |
| #7 | 14.25 x 20 | Laptop up to 15 in, art prints, large softcover collections |
Two things move a size decision beyond the fit. First, the inside is smaller than the outside by roughly a quarter inch of bubble lining on each edge, so a book that measures 8.5 x 11 sits inside a #4 but not a #3. Second, a mailer bulging more than about a quarter inch draws USPS's non-machinable rule and prices as a parcel; the numbers all move up when that happens.
Where the numbering does and does not match
The #000 to #7 numbering is a convention. Every mailer maker follows it in spirit and diverges in the second decimal.
Generic reboxers
Warehouse-club and marketplace mailers round the dimensions and occasionally add a quarter inch to fit a house film. Buy one pack of a size before ordering a case; a #5 that measures 10.75 x 16.25 costs the same to buy and can tip the parcel into the next USPS band.
The kraft-lined variant
Kraft mailers with an interior bubble film are numbered the same but weigh a little more. On sub-$8 shipments the extra ounces move the label between weight bands more often than the bubble content does.
Common size choices, with the item that anchors them
Small jewellery, #000
A single ring, a pair of earrings in a jeweller's box, small findings. Include a tissue wrap; the mailer alone gives no impact protection and rings are the classic loss item on a padded envelope.
Books, #2 or #4
Trade paperbacks sit inside a #2 with a card in the fold; hardcovers up to 9 x 12 sit inside a #4 with a book board on the front to defend the corners. Above that, use a small box.
Small apparel, #4 or #5
A folded t-shirt or a light hoodie moves comfortably in a #4 or #5. Our poly mailer against a box guide tested the bag-and-box choice on the same shirt across the same lane; the mailer won each row.
Where to price the parcel
Weight decides the label more than the mailer size does, up to around 2 lb. Our bubble mailer shipping guide priced a paperback in a padded mailer with UPS Ground Saver on 2026-07-27 and a lighter 0.4 lb flat on the same lane. Type the item and the two ZIPs into the calculator and the full five-row menu comes back for the parcel you actually have.
Where these numbers come from
- Uline, individual product listings for #0, #1, #2, #3, #4 and #5. Read 2026-08-11.
- PackagingSupplies, bubble mailers size chart for #000 and #00 outside and inside dimensions. Read 2026-08-11.
- USPS non-machinable rules cited on our sister mailer guides; the Domestic Mail Manual reference is at pe.usps.com.
Sizes are trade practice and can drift a quarter inch between makers. Treat the chart above as a working reference and measure the mailer that landed on your shelf before ordering a case.
Bubble mailer size questions
What size is a #000 bubble mailer?
4 by 8 in outside dimensions, roughly 3.75 by 6.5 in usable inside, per the PackagingSupplies bubble mailer size chart read 2026-08-11. #000 fits a small jewellery box, a single ring, a small phone case.
Which bubble mailer size fits a paperback book?
A #0 at 6 by 10 in fits a mass-market paperback; a #2 at 8.5 by 12 in fits a trade paperback with room for cushioning. Larger sizes accommodate hardcovers.
What is the largest standard bubble mailer size?
#7 at 14.25 by 20 in outside is the largest number in the standard set. Beyond that, sellers move to bubble-lined kraft mailers cut to order, or to small boxes with an internal bubble bag.
Does the sizing chart match every brand?
The #000 through #7 numbering is an industry convention, not a single spec. Uline, Sealed Air and generic re-boxers vary the outside by a quarter inch here and there. Buy one pack of a size to test before ordering a case.
Does USPS surcharge non-machinable bubble mailers?
USPS charges a non-machinable letter surcharge on pieces above certain dimensions or with rigid or lumpy contents. Once a mailer bulges more than a quarter inch, or reads over 3.5 oz for a letter, it prices as a Ground Advantage parcel rather than a letter, which is where our poly and bubble mailer guides sit.