Carton Box Guide · Material
Carton Box Material: Corrugated Sheet, Paper, Grammage & Flute
A box's strength, look, and cost are all decided at the material level — from the structure of the corrugated sheet, to the type of paper, to the grammage (gsm), to the flute profile used.
Corrugated Sheet: What a Box Is Made of
A corrugated sheet isn't plain cardboard. Its basic structure is three layers: two liners (the flat outer and inner paper) sandwich one fluted medium in the middle. The liners resist pulling and puncturing; the fluted medium is what absorbs pressure and cushions impact.
Single, Double, Triple Wall
The number of layers decides how much load the sheet can hold. More layers means more strength and more thickness.
Single wall
One medium between two liners. The most common structure — enough for the majority of shipping boxes.
Double wall
Two mediums and three liners. Stronger and more stack-resistant. For heavy parts or tall stacks.
Triple wall
Three mediums and four liners. Very strong — sometimes a replacement for a wooden crate on very heavy goods.
Paper Types: Kraft, White Kraft, Medium
Three paper types make up a sheet — two for the liners, one for the medium.
Kraft
Natural brown, with the wood fibre visible. The strongest and most economical of the three. Suited to industrial and functional needs.
White kraft
A clean white surface for a neater, more modern look, with strength on par with brown kraft. The print surface is sharper; it costs a little more.
Medium
The fluted paper in the middle, not visible from the outside. It doesn't show on the finished product, but it's the main determinant of a box's structural strength.
Grammage (gsm / Substance Weight)
A paper's weight and thickness are measured in grams per square metre (gsm). The higher the gsm, the stronger and the more expensive per metre. But a higher gsm can sometimes save money, because it takes less total material to reach the same strength.
Getting the substance weight right matters for three reasons: strength & protection (preventing damage in transit and under stacking), cost efficiency (thicker isn't always better), and appearance (a box that feels solid raises the perceived value of what's inside).
Example
- Single wall, flute E, 120 gsm liner → total thickness around 3.5 mm.
- Single wall, flute B, 150 gsm liner → total thickness around 5 mm.
The figures above are illustrative. We set the actual gsm from the weight, dimensions, and how the part is stacked — not one number for everything.
Flute Profiles
The flute is the wave shape in the medium. The taller the flute, the thicker the cushioning — but the more space and paper it takes. The tighter it is (a small flute like E), the smoother the surface for printing.
| Flute | Height (approx.) | Best suited to |
|---|---|---|
| E | ~1.5 mm | Small boxes, light parts; the smoothest print surface |
| B | ~3 mm | General-purpose boxes, crush- and puncture-resistant; single wall |
| C | ~4 mm | Medium–large boxes; better cushioning and stacking strength |
| BCdouble wall | ~7 mm | Heavy parts, tall stacks, long-distance shipments |
Most automotive parts sit comfortably at B or C; double wall BC is for heavy parts or tall stacks.
Inside Dimensions vs Outside Dimensions
Two related numbers with a different focus. Quoting the wrong one when you order is one of the most common causes of a box that doesn't fit.
Inside dimensions
The empty space inside the box (internal length × width × height). This decides whether the part fits and sits right — tight enough that it doesn't move, loose enough that it's easy to pack. This is the number that protects the part.
Outside dimensions
The total dimensions including wall thickness. This decides space efficiency, shipping cost, how many boxes fit per pallet/truck, and how the box looks on a shelf. This is the logistics number.
Inside dimensions protect the part; outside dimensions drive cost and handling. We calculate both from your part's dimensions and the wall thickness chosen.
See it directly
What we make, under one roof.
Corrugated carton box and PE/PP polybag, built to your part spec — from 500 pcs.