Two boxes labelled 12x9x6 can be different sizes. One supplier is quoting the inside, another is quoting the outside, and the difference is the board. Before anything else, fix which convention you are working in, because the rest of this page depends on it.
The convention
Corrugated boxes are described length by width by depth. Length is the longer side of the open face, width is the shorter side of the open face, and depth is the distance from that opening down to the base. The figures are inside dimensions, meaning the usable interior. Outside dimensions add the board thickness on both sides of each axis, so a single wall box gains roughly an eighth of an inch per side on B flute and less on E flute. That sounds trivial until a carrier's dimensional threshold is a quarter inch away.
Common sizes buyers start from
| Inside size (inches) | Typically used for |
|---|---|
| 6 x 6 x 6 | Small single items, mugs, candles, jars |
| 8 x 8 x 8 | A single mid-size product with void fill |
| 10 x 10 x 10 | Multi-item orders, small kits |
| 12 x 9 x 6 | Books, flat goods, mixed small orders |
| 12 x 12 x 12 | The default general purpose cube |
| 14 x 14 x 14 | Bulkier single items and multi packs |
| 18 x 18 x 18 | Light bulky goods, soft goods, gift hampers |
These are starting points from general trade practice, not an iBox stock list. Every box we make is drawn to the size you specify, which is usually the better answer, because a box built to your product removes void fill and the freight cost of shipping air.
Measuring for a custom size
- Measure the product at its true maximum on each axis, including any handle, spout or lid that sticks out.
- Add the protective layer you intend to use, whether that is a wrap, a corner pad or an insert.
- Add a small working clearance so the box can be packed quickly, not wrestled shut.
- If you are packing more than one unit, decide the arrangement first, then measure the arrangement rather than the item.
- Check the finished outside dimensions against your carrier's size and dimensional weight rules before you approve the dieline.
Board and flute
Flute is the wave layer inside corrugated board, and the letter tells you its profile. E flute is the thinnest of the common profiles and prints well, B flute is a middle ground with better crush resistance, and C flute is thicker again with more cushioning. Thicker board means a larger outside dimension for the same interior, so flute is a dimensional decision as well as a strength decision. The detail is on what is flute in corrugated, and further size references are on corrugated box dimensions.
A note on carrier billing
Carriers bill on the greater of actual weight and dimensional weight, which is calculated from the outside dimensions. Divisors change and vary by service and account, so confirm the current figure with your carrier rather than assuming last year's number. This is the single most common reason a slightly oversized box quietly costs money on every shipment.
Ordering a custom size
The minimum is 100 boxes and bulk pricing starts at about $0.48 per unit, confirmed on your written quote once size, board and print are fixed. The die and plates, design support, free US shipping and a digital proof before printing are included. 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, with specialty imported items running up to about 12 weeks.
If your product is going into a branded mailer rather than a plain shipper, see custom mailer boxes. Otherwise send your three measurements and quantity to /quote/ and we will confirm the inside and outside dimensions on the proof.
