Single wall corrugated is one fluted medium glued between two liners. That single layer is the whole sizing problem, because it is the thing standing between the number you measured on your product and the number the die is cut to. There is no universal single wall size chart worth trusting, so the reliable approach is a method: pick the flute, measure the product, state the internal dimension, and let the die follow.
Flute caliper is the number that moves your size
Board caliper is one of the few published figures in corrugated, and it is the one that matters at the sizing stage. Every flute profile has an approximate thickness, and a finished box grows by about two walls of that thickness across each axis.
| Flute | Approximate caliper | Where single wall in this flute usually lands |
|---|---|---|
| A | About 1/4 in | Light, bulky goods that need stacking height more than crush resistance |
| B | About 1/8 in | Die cut inner packs and boxes that have to resist crush on a shelf |
| C | About 3/16 in | The general shipping grade behind most ecommerce cartons |
| E | About 1/16 in | Printed retail boxes and mailers where the graphics lead |
| F | About 1/32 in | Small retail boxes that want a corrugated feel at near carton thinness |
Treat that as arithmetic. A box with a 10 in internal width built in C flute measures roughly 10 3/8 in across the outside, because you add about 3/16 in of board at each side. The same internal width in E flute measures about 10 1/8 in. If you are fitting a box into a fixed space, a mailbox slot, a shipper or a shelf, that difference is the difference between fitting and not.
The measuring method
- Measure the product at its widest point, including caps, handles, hinges and anything that protrudes.
- Add clearance for whatever goes around it: an insert, a bag, tissue, or void fill on all four sides.
- Write the result as internal length x width x depth, in that order, with the opening on the length by width face unless you say otherwise.
- Say the word internal on the request. Suppliers quote both, and a box quoted external is a box that arrives smaller inside than you planned.
- If you are unsure of the flute, send the filled weight and how it ships instead. Weight and drop height pick the board better than a guess does.
Industry starting points, not our stock list
If you are working backwards from something you already ship, published references give a sane anchor. US letter paper is 8.5 x 11 in and ISO A4 is 210 x 297 mm, which set a floor for anything document shaped. The standard US pallet is 48 x 40 in, so a box footprint that divides evenly into 48 x 40 travels with less wasted cube. Those are industry figures you can check anywhere. They are not iBox Factory stock sizes, and nothing here is a size we hold on a shelf.
Minimum, price and production lanes
The minimum on custom single wall is 100 boxes, priced from about $0.48 per unit at bulk volumes and confirmed on your written quote. The die, the plates, design support, US shipping and a digital proof before anything prints are included, which is exactly why a custom internal size is not a premium. Production runs in three lanes and is quoted per product: rush (expedited production plus air freight), standard (air), and cost saver (sea). The floor is from about 7 business days, plus 2 to 5 for delivery, and specialty imported work can run up to about 12 weeks. Boxes are made at two plants, West Chicago in the US and Guangzhou in China.
Measure your product at its widest point, decide how much clearance the insert or void fill needs, and send those three numbers with your quote request. If you already know you are ordering single wall shippers rather than specifying them from scratch, corrugated boxes is the page to order from, and we will confirm internal versus external on the proof.
