A literature mailer is sized backwards from a sheet of paper. Get the flat sheet dimension and the stack thickness right and everything else follows, because unlike most packaging there is no awkward shape to design around. The only real risks are sizing it too tight, so the contents buckle, or too loose, so they slide and the corners get chewed.
Step 1: fix the flat dimension
Decide what goes inside at its final folded size. If a letter sheet ships flat, your flat dimension is 8.5 x 11 in. If it is tri-folded, it becomes roughly 8.5 x 3.67 in and you are packaging a completely different shape. These are the published paper sizes to work from.
| Flat sheet | Size | Internal footprint with 1/8 in clearance |
|---|---|---|
| US letter | 8.5 x 11 in | About 8.75 x 11.25 in |
| US legal | 8.5 x 14 in | About 8.75 x 14.25 in |
| Tabloid | 11 x 17 in | About 11.25 x 17.25 in |
| ISO A4 | 210 x 297 mm | About 213 x 300 mm |
| ISO A5 | 148 x 210 mm | About 151 x 213 mm |
These are the published paper standards with a clearance allowance applied. They are a starting point for your own calculation, not an iBox stock size list.
Step 2: measure the stack, do not calculate it
Paper thickness varies enormously with weight and coating. As a rough planning figure, ordinary office stock runs around 0.004 in per sheet, so a ream of 500 sits near 2 in. A heavy coated brochure stock can be double that per sheet. The reliable method takes thirty seconds: assemble the exact contents you will mail, press them lightly together, and measure the stack with a ruler or calipers. Add about 1/16 in so the mailer closes without stressing the score.
Step 3: choose the construction
Flat contents get packed three common ways, and the choice changes the size you need.
- Flat mailer or envelope style. Minimum material, minimum depth, no protection at the corners. Good for a few sheets.
- Book wrap. A blank that folds around the stack and locks, so the depth adjusts to the contents. Good when the sheet count varies between orders.
- Die cut mailer with a tuck front. A fixed depth box with a clean unboxing. Good when the contents are a fixed kit and presentation matters.
Book wrap is the one worth knowing about if your page count is not fixed, because it removes the need for a second size.
Step 4: check the postage envelope before the mailer
Flat mail is priced by dimension and thickness as well as weight, and the thresholds are set by the carrier rather than by the packaging supplier. Confirm the current rate bands with your carrier before you fix a depth, because a mailer that is a fraction over a threshold can cost more to send than it did to make. This is worth doing before the die is cut, not after.
Step 5: state it properly on the spec
Write the result as internal length x width x depth and say the word internal. On a thin mailer the difference between internal and external is small in absolute terms but large as a proportion, and a mailer that is 1/8 in too tight will not take the contents at all.
How ordering works
Literature mailers start at 100 units, priced from about $0.48 per unit at bulk volumes and confirmed on your written quote. The cutting die, the printing plates, design support, US shipping and a digital proof are included. That is the reason a mailer cut exactly to your stack is not a premium option: there is no tooling charge you are avoiding by rounding to a near standard size. Turnaround is stated per product in three lanes, rush (expedited production plus air freight), standard (air) and cost saver (sea), from about 7 business days of production plus 2 to 5 days for delivery.
Send the flat sheet size and a measured stack thickness and we will come back with a dieline. Start at request a quote, browse formats on the mailer boxes page, or if you are still choosing a style, read what size literature mailer do I need.
