The direct answer is that a literature mailer is sized by the flat dimension of its contents plus a small clearance, and the only genuinely difficult part is deciding which format you want. Four questions settle it.
1. What exactly is going inside?
Not the campaign, the physical items. A single tri folded letter is a completely different object from a twenty page brochure, a sample swatch and a business card. List everything, including the reply envelope people forget. If any item does not fold, the mailer has to accommodate it flat.
2. Flat or folded?
A US letter sheet mailed flat needs a mailer of roughly 8.75 x 11.25 in inside. Tri fold that same sheet and it becomes about 8.5 x 3.67 in, which fits a long narrow mailer instead. Neither is better. Flat looks more considered and costs more to send. Folded is cheaper and arrives creased. Decide which trade you are making before you look at any dimensions.
3. Is the page count fixed or variable?
This is the question that saves the most money, and it is the one most often skipped. A fixed depth mailer works beautifully when every mailing holds the same contents and terribly when it does not, because you end up either buying two dies or shipping half empty boxes.
| If your contents are | Choose | Why |
|---|---|---|
| Identical every time | Die cut mailer with a fixed depth | Tightest pack, best unboxing, no wasted volume |
| Varying by a few sheets | Book wrap | The wrap folds down to the actual stack, so one size covers a range |
| Always just one or two sheets | Flat mailer or envelope style | Minimum material and minimum postage band |
| Mixed items including a sample | Mailer with a tray or a die cut retainer | Stops the sample sliding and creasing the print |
4. How is it being sent?
Flat mail is priced on dimension and thickness as well as weight, and the thresholds belong to the carrier, not the packaging supplier. Confirm the current bands with your carrier and design under whichever one you are aiming for. A pack that sits a fraction over a band costs more to send for the entire campaign, which usually dwarfs any saving on the box itself.
Reference sizes to work from
These are the published paper standards, which are where the flat dimension comes from. They are a reference point for your calculation rather than an iBox stock size list.
| Contents | Flat size | Suggested internal footprint |
|---|---|---|
| US letter, flat | 8.5 x 11 in | About 8.75 x 11.25 in |
| US letter, tri folded | About 8.5 x 3.67 in | About 8.75 x 3.9 in |
| US legal, flat | 8.5 x 14 in | About 8.75 x 14.25 in |
| ISO A4, flat | 210 x 297 mm | About 213 x 300 mm |
| ISO A5, flat | 148 x 210 mm | About 151 x 213 mm |
The depth is the one number you have to take from your own contents. Assemble the pack, press it lightly together, measure it, and add about 1/16 in. If you want the full procedure rather than the decision, it is set out on how to size a literature mailer.
What it costs and how long it takes
Literature mailers start at 100 units, from about $0.48 per unit at bulk volumes, confirmed on your written quote. The cutting die, the printing plates, design support, US shipping and a digital proof are included, which is why a mailer cut exactly to your contents is not a premium option. 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. Rush carries a premium of roughly 7 to 25% depending on the job.
Tell us what is going in the pack and whether the contents vary, and we will recommend a format and a size. Start at request a quote, or browse constructions on the mailer boxes page.
