GSM stands for grams per square metre. Take a sheet one metre by one metre, weigh it, and the number in grams is the GSM. That is the whole definition, and understanding what it leaves out is more useful than the definition itself.
GSM is weight, not thickness
It is tempting to read a higher GSM as a thicker board, and most of the time that is roughly true. But it is a measure of mass per area, and two boards at the same GSM can differ noticeably in thickness because they differ in bulk. A bulky, lightly compressed board is thicker and stiffer per gram than a dense, heavily calendered one. If what you actually care about is how rigid the box feels in the hand, GSM alone will not tell you.
The complementary measure is caliper, the physical thickness of the sheet. In US packaging this is often quoted in points, where one point equals one thousandth of an inch. Specify both if stiffness matters to you, and ask for a physical sample rather than trusting a number on a page.
Where GSM applies, and where it does not
| Material | How it is specified |
|---|---|
| Folding carton board | GSM, often alongside caliper in points or microns |
| Paper bags and wraps | GSM |
| Rigid box wrap paper | GSM |
| Corrugated board | Flute and board grade, not GSM |
That last row catches people out. When you move from a printed carton to a corrugated shipper, GSM stops being the language. Corrugated gets its stiffness from the fluted middle layer, so it is described by flute size and by the grade of the liners and medium. Asking a corrugated supplier for a GSM is like asking for the thread count of a plank.
How to choose a board weight without guessing
- Start from the load. What does the box have to carry, and does anything stack on it?
- Start from the structure. A tall narrow carton needs more stiffness than a shallow one at the same weight of contents.
- Start from the finish. Heavy foil, embossing and thick laminates all work better on a board with some body behind them.
- Then ask for samples in two adjacent weights and handle them. Five minutes with two physical samples beats an hour of comparing numbers.
What to write on a quote
Write the GSM if you know it, the caliper if stiffness matters, the finish you intend to apply, and what the box has to hold. If you do not know the board, describe the job instead and ask for a recommendation with samples. Describing the job honestly always produces a better board than guessing at a number.
Ordering
Minimum order is 100 boxes, and pricing starts from about $0.48 per unit at bulk volumes, confirmed on your written quote. The die and plates, design support, US shipping and a digital proof before anything prints are included. Turnaround is quoted per product in three lanes: rush with expedited production and air freight, standard by air, and cost saver by sea, from about 7 business days, plus 2 to 5 for delivery. Specialty imported items can run up to about 12 weeks. Production is in West Chicago and in Guangzhou.
If your board choice is being driven by recyclability, is kraft paper packaging recyclable covers what actually affects acceptance. For unbleached kraft stock itself, see kraft boxes. Describe your product and your load when you request a quote and the board comes back recommended rather than assumed.
