A corrugated shipping box is specified as length x width x depth, measured inside, in that order. Length is the longer of the two opening dimensions, width the shorter, depth the distance from the bottom score to the top score. Get that order wrong on a purchase order and you will receive a box that is technically correct and practically useless, so it is worth being pedantic about it.
Internal versus external, and why the difference matters
Internal dimensions are the usable space. External dimensions are what the carrier measures and what the pallet sees. The gap between them is the board caliper, doubled, on each axis. On a thin E flute retail shipper the gap is small. On a double wall carton it is enough to push a load over a pallet edge. Ask which one your quote is stating, every time, and put the answer on the drawing.
Flute calipers you can plan around
Flute is the wave of paper between the liners. These are the industry standard profiles, not an iBox stock list, and they are the figures to use when you are estimating outside size before a dieline exists.
| Flute | Approximate caliper | Typically used for |
|---|---|---|
| E | About 1/16 inch | Printed retail shippers and small mailers |
| B | About 1/8 inch | Die cut boxes needing crush resistance over cushioning |
| C | About 3/16 inch | The general ecommerce and shipping workhorse |
| A | About 1/4 inch | Cushioning and stacking on bulky, light contents |
| BC double wall | About 5/16 inch | Heavy contents, long transit, repeated handling |
How to arrive at your internal dimensions
- Measure the product at its widest point on each axis, including anything that sticks out: a lid lip, a handle, a cap, a flange.
- Add clearance for whatever goes around it. A thin poly bag needs almost nothing. A corrugated insert adds its own caliper on both sides. Air pillows or paper void fill want at least an inch of working room where cushioning is needed.
- Write the result as length x width x depth and label it internal.
- Check the footprint against the pallet before you commit. Boxes are cheap. Shipping air is not.
Pallet and carrier arithmetic
The standard North American pallet deck is 48 x 40 inches. A footprint that tiles that deck with little overhang gives you a stable column and a lower freight cost per unit. Parcel carriers charge on dimensional weight, which is calculated from the outside dimensions, so a half inch of unnecessary width on every box is a bill you pay on every shipment for the life of the SKU. If you want the full treatment of that tradeoff, read what cube utilization is before you finalise the drawing.
Ordering, minimums and lead time
The minimum on custom corrugated is 100 boxes. Pricing starts from about $0.48 per unit at bulk volumes and is confirmed on your written quote, never guessed from a chart. Turnaround is quoted per product in three lanes: rush, which is expedited production plus air freight and carries a premium of roughly 7 to 25 percent depending on the job, standard on air, and cost saver on sea. The floor is about 7 business days in production plus 2 to 5 days for delivery, and specialty imported constructions can run up to about 12 weeks. Production runs out of two plants, West Chicago in the United States and Guangzhou in China.
The cutting die, the printing plates, design support, US shipping and a digital proof before anything prints are included. That is the part that changes how you should think about sizing: a genuinely custom internal dimension costs no more to tool than one that happens to sit near a common size, so size the box to the product rather than bending the product to fit a box. To order the board itself, see corrugated boxes, or start a quote with your product dimensions and we will come back with internal sizes, a board spec and a lead time in writing.
