An envelope box is the format for anything flat that must not bend: prints, documents, photographs, apparel, jewelry on a card, thin electronics. It sits between a paper envelope, which offers no rigidity, and a shipping carton, which costs more and takes more space. The sizing logic is different from a cube shaped box, so it is worth understanding before ordering.
Standard faces
| Face size (in) | Holds | Note |
|---|---|---|
| 6 x 9 | Small documents, jewelry cards, accessories | Compact and cheap to ship |
| 9 x 12 | Unfolded letter documents, small prints | The most requested face |
| 10 x 13 | Folders, catalogs, apparel | Fits a letter document with clearance |
| 12.5 x 9.5 | Photographs and print orders | Landscape orientation for framed print sizes |
| 13 x 18 | Large prints, posters flat packed | Check carrier oversize thresholds before committing |
Depth is normally between about 1/4 inch and 1 inch. Beyond that the format stops behaving like a flat mailer and a shallow shipping box becomes the better structure.
Why thickness is a pricing decision
Postal and carrier rate structures treat flat items and parcels differently. As a working rule, US Postal Service flats are generally limited to around 15 x 12 x 3/4 inches, and anything thicker or more rigid than that gets handled and priced as a parcel. Carrier rules change, so confirm current limits with your carrier before you finalize a die. If your contents fit inside those limits, a quarter inch of unnecessary depth can move an entire shipping program into a more expensive category.
Rigidity is the actual job
A flat mailer fails when it bends, not when it is crushed. Three specification choices control that:
- Board caliper or flute. E flute corrugated resists bending far better than folding carton board at similar thickness.
- Flute direction. Running the flutes across the short dimension stiffens the panel against the way it naturally folds.
- A stiffener. A chipboard pad inside is cheaper than upgrading the whole mailer, and it is how most print sellers ship photographs.
The related structures are covered on literature box dimensions, and if the contents turn out to need real depth, compare against custom mailer boxes.
Closures
A tuck flap is standard and reusable, which suits returns. A peel and seal adhesive strip is faster to pack and single use. A tear strip makes opening easy and destroys the mailer, so avoid it where a customer may need to send the item back. Pick the closure around the return policy, not around the packing bench.
Minimum, price and turnaround
Minimum order is 100 units, and because the die is included, a face size cut to your product costs no more in tooling than a standard one. Unit pricing opens at about $0.48 per unit at bulk volumes and the exact figure is on your written quote. Turnaround is stated per product across three lanes: rush pairs expedited production with air freight at a premium of about 7 to 25% depending on the job, standard runs by air from about 7 business days plus 2 to 5 days for delivery, and cost saver moves by sea. Design help, free US shipping and a proof before print come with it.
Send the dimensions of the flattest and the thickest thing you ship to our quote form and we will size one mailer that handles both.
