A poly mailer is sized flat: width first, then length, both measured on the outside of the finished bag. That is the reverse of how boxes work, where the number that matters is the internal dimension. Get the convention wrong and you order a bag an inch too tight to seal. This page gives the widths the trade uses, then the method for deriving your own.
Industry-typical poly mailer sizes
These are the sizes that have become common across the mailer trade, published widely enough to be a safe starting point. They are not an iBox Factory stock list, and none of them costs more to change, because the tooling is included in the job.
| Flat size (in) | Typically used for |
|---|---|
| 6 x 9 | Jewellery pouches, single accessories, thin printed matter |
| 9 x 12 | A folded shirt, a small soft-goods order, document packs |
| 10 x 13 | The general ecommerce workhorse for apparel |
| 12 x 15.5 | Two or three garments, bulkier knitwear |
| 14.5 x 19 | Bedding sets, hoodies, multi-item orders |
| 19 x 24 | Bulk soft goods, pillows, large multipacks |
Deriving your own width and length
- Fold or stack the item exactly as it will leave your bench, including any tissue, card or return label.
- Measure the widest point of that stack, not the garment laid flat.
- Add about an inch to the width so the side seals are not under tension when the bag is full.
- Add 1.5 to 2 inches to the length for the adhesive flap and its liner.
- If the item is thick, add its thickness again to both width and length. A flat bag has to wrap around depth it was never given.
If the resulting number lands near one of the sizes above, take the standard. If it does not, order the number you actually measured. A genuinely custom flat size costs no more to tool than a near-standard one.
Gauge, which decides more than size does
Film thickness is quoted in mils. Soft, forgiving goods sit at the thin end. Anything with a corner, a zip pull or a hard edge needs more. Co-extruded film gets more tear resistance out of the same thickness than single-layer film, so ask what construction you are being quoted, not just the number.
- Around 2 mil: light apparel, soft accessories, low-value contents.
- Around 2.5 to 3 mil: the common ecommerce range for mixed soft goods.
- 4 mil and up: heavier loads, sharp-cornered contents, longer transit legs.
What a quote needs from you
Flat width and length, gauge or a description of the contents and their weight, whether you want a tear strip, a second adhesive strip for returns, and your artwork or a rough layout. Design support is included, so a sketch is enough to start. A digital proof goes out before anything prints.
Minimum order is 100 units, and pricing starts from about $0.48 per unit at bulk volumes, confirmed on your written quote. Production runs out of two plants, West Chicago in the US and Guangzhou in China, and turnaround is quoted per job in three lanes: rush (expedited production plus air freight), standard (air) and cost saver (sea), from about 7 business days plus 2 to 5 for delivery. Rush adds about 7 to 25% depending on the job.
One thing to check before you commit
Mailers are billed by carriers on dimensional weight as well as actual weight once they get bulky, so a bag that is generously oversized can cost more to ship than the packaging saved. Our page on dimensional weight shows the arithmetic. If the contents turn out to need structure rather than a film bag, compare against the mailer box guide.
Send us the flat size you measured, the gauge you think you need and roughly what you are shipping, and we will come back with a written quote on the quote form. If you are unsure between two sizes, say so and we will price both.
