Sizing a shipper is a sequence, not a lookup. Work through it in order and the number at the end is defensible: measure the load, add the protection, set the board, then test the result against what it will cost to ship and to palletise.
Step one: measure the load, not the product
The load is the product as it leaves your packing bench, including any retail carton, literature, invoice, accessories and dunnage that travels with it. Measure that assembly at its widest point in each axis. If several units ship together, build the actual arrangement and measure the block, because units nest differently than they multiply.
Step two: add the protection
Whatever protects the product has thickness, and that thickness is part of the internal dimension.
| Protection | Add per side |
|---|---|
| Loose fill or paper void fill | The cushion depth you want, on all four sides and top and bottom |
| Foam end caps or corner blocks | The cap depth on the two faces they sit on |
| Bubble cushioning wrap | The wrapped thickness, typically counted twice per axis |
| A fitted insert or moulded tray | The insert wall thickness where it contacts the box |
A useful rule of thumb: if you are using loose void fill, budget a consistent cushion on every face rather than a generous one on top and nothing at the sides, because a box drops on its corner, not its lid.
Step three: state it properly
Write the result as internal length x width x depth. In corrugated, length is the longer of the two dimensions of the opening and depth is the height from opening to base. Say internal explicitly, and ask for the quote to confirm it. On double wall board the gap between internal and external is enough to ruin a fit, and this is the single most common source of a wrong box.
Step four: choose the board from load, not category
Flute profile describes the wave inside the board: E flute is about 1/16 inch and prints well, C flute at about 3/16 inch is the ordinary shipping grade, A flute at about 1/4 inch cushions and stacks, B flute at about 1/8 inch resists crush, and double wall combines two. To get the grade right, send two numbers: the packed weight of one box, and how high the boxes will be stacked on a pallet or in a rack. Compression failure happens to the box at the bottom of a stack after a week in a warehouse, not on day one.
Step five: test the result against the bill
- Dimensional weight. Carriers bill the greater of actual and dimensional weight, so a box with two inches of unnecessary air on each axis is charged on every shipment for its whole life. The arithmetic is on our dimensional weight page.
- Pallet fit. The standard US pallet is 48 x 40 inches. A box that tiles that footprint cleanly ships more units per pallet than one that is two inches wider and leaves a gap you pay to move.
- Case count. If the shipper goes into a master case, check that the outer dimension divides sensibly into the case you already buy.
Ordering
Custom corrugated starts at a 100 box minimum, from about $0.48 per unit at bulk volumes, confirmed on your written quote. The die, the plates, design support, US shipping and a digital proof before anything prints are included. That last point is the reason this method is worth following: because the tooling is included, the exact internal dimension you calculate costs no more to make than a nearby round number, so there is no reason to compromise the fit. We make in West Chicago in the US and Guangzhou in China, and turnaround is quoted per product 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.
Order at custom shipping boxes. If the box will be a regular slotted container, the flap geometry on sizing a regular slotted box is the next thing to read.
Send the load measurement, the protection you plan to use and the packed weight through the quote form, and we will come back with an internal dimension, a board grade and a written price.
