A die cut mailer is a one piece corrugated box that folds up without tape and closes with a tuck flap. Because it is die cut, the internal size can be anything you want, which is exactly why people get stuck. There is no chart to pick from. There is a method.
The five steps
- Measure the product at its widest point. Not the box it came in, not the label panel, the widest actual point of the thing you are shipping. Do it with the product packed as it will ship, including any bag or tissue.
- Add clearance for the protection. Tissue and a sticker add almost nothing. A pad or a folded insert adds its thickness on both sides. Air pillows or paper void fill want a half inch or more per side to actually do anything.
- Set the depth from the packed stack. Put everything that goes in the parcel in a pile and measure the pile: product, card, sample, return slip. That height plus a small allowance is your depth. Depth is the dimension people guess, and the guess is almost always too generous.
- Write it as internal length x width x depth. Longest dimension first. Then say the word internal on your quote request so nobody has to assume.
- Check it against dimensional weight before you commit. Multiply length by width by depth in inches and divide by your carrier's divisor. US parcel carriers commonly use 139 for domestic retail rates. If the dimensional weight beats the actual weight, the parcel is being billed on air and a shallower mailer pays for itself.
Board choice for a mailer
Die cut mailers are usually E flute or B flute. E flute is about 1/16 in (1.6 mm) per wall, prints beautifully and folds crisply, which is why most branded ecommerce mailers use it. B flute is about 1/8 in (3.2 mm) and carries more weight, at the cost of a slightly softer print surface and a thicker fold. If the product is heavy or the parcel will be stacked, B flute. If the product is light and the unboxing matters, E flute.
Remember that flute is added to the outside. A mailer specified at 9 x 6 x 2 in internal in B flute is roughly a quarter inch larger on each outside face, which can matter if you are trying to stay under a carrier threshold or fit a fixed shelf.
Common anchors worth knowing
| Reference | Size | Why it comes up |
|---|---|---|
| US letter | 8.5 x 11 in | Print, documents, folded apparel on a letter footprint |
| ISO A4 | 210 x 297 mm (8.27 x 11.69 in) | The same job outside the US |
| US letter, flat with margins | Around 9 x 11.5 in internal | So a sheet drops in without bending |
These are published industry reference dimensions and a starting point only. They are not iBox stock sizes, and we do not publish a stock mailer chart.
Why custom costs no more to tool
The cutting die is included, along with the plates, design support, US shipping and a digital proof before anything prints. So a mailer at 9.25 x 6.5 x 1.75 in internal, cut to your product, costs no more to tool than a rounded size. On a mailer that ships thousands of times, the right depth beats a round number every time.
Ordering and turnaround
Minimum order is 100 mailers, from about $0.48 per unit at bulk volumes, confirmed on your written quote. Production runs in three lanes: rush (expedited production with air freight), standard (air) and cost saver (sea), from about 7 business days plus 2 to 5 for delivery, with specialty imported items up to about 12 weeks. Rush carries a premium of about 7 to 25% depending on the job. We produce in West Chicago and Guangzhou.
If you would rather work from the product outward than from a method, our companion page on what size die cut mailer you need works through it by category. To order, see mailer boxes.
Measure one product, take the packed stack height, and send both with your monthly volume when you request a quote. We will confirm the flute and tell you if a quarter inch off the depth changes your freight band.
