The one piece folder, often shortened to OPF, is cut and creased from a single sheet with no glue joint. You size it the way you size any folding carton, from the internal cavity out, but an OPF has one extra number that matters to your price: the flat blank it is cut from. There is no universal OPF size chart, so this page covers both numbers and how they relate.
The two dimensions of an OPF
The first is the cavity. Measure your product at its widest, add clearance, and write it as internal length x width x depth. The second is the blank, the flat die-cut sheet before anyone folds it. Because an OPF wraps up and over the product, the blank has to carry the base panel plus both side walls plus the end flaps.
As a working approximation, the blank runs about the internal length plus twice the depth plus a flap allowance in one direction, and about the internal width plus twice the depth in the other. Corrugated is quoted by the square area of board consumed, so a small change in depth can move your unit cost more than a change in length. If you are choosing between two depths, ask for both on the quote and compare.
Depth is the constraint, not length
An OPF folds flat and holds its shape by friction and the end flaps rather than a glued corner. That makes it excellent for flat rigid goods and poor for tall or squishy ones.
| Product type | Fits an OPF well? | Why |
|---|---|---|
| Books, printed boards, framed art | Yes | Flat, rigid, low depth, the wrap holds tight against the faces |
| Apparel sets, multi-item kits | Sometimes | Only if the stack is compressed and consistent, otherwise the flaps bow |
| Tall bottles, jars, anything cylindrical | No | Depth exceeds what the folded walls can hold square |
Paper anchors you can size against
If your product is print, the published sheet standards are a useful starting point rather than a guess. US letter is 8.5 x 11 in. ISO A4 is 210 x 297 mm. A US trade paperback commonly trims to 5.5 x 8.5 in. Those are industry-typical figures, not iBox stock sizes, but they give you a defensible baseline to add clearance to. Add enough that the product does not bind when the flaps close, and remember that on double wall board the walls themselves consume more of the cavity.
Ordering an OPF
Minimum order is 100 boxes. Pricing starts from about $0.48 per unit at bulk volumes and is confirmed on your written quote once board grade and print coverage are set. The cutting die and the printing plates are included, along with design support, US shipping and a digital proof before anything prints. That matters on an OPF more than on most styles, because the folder relies on crease positions being right, and a proof is where you catch a crease that is a sixteenth of an inch off.
The three production lanes are rush (expedited production plus air freight, at a premium of about 7 to 25% depending on the job), standard (air) and cost saver (sea), from two plants in West Chicago and Guangzhou. The floor is from about 7 business days, plus 2 to 5 for delivery.
If your product is a book or a flat print item, the sizing walkthrough on how to size a book wrap mailer covers the crease-per-thickness question in more detail, and the mailer boxes page shows the glued alternatives. Send your internal dimension, your product weight and a rough annual volume through the quote form and ask for the OPF and a tuck style side by side.
