Also known as: Grams per Square Metre, Grammage, g/m²
GSM (grams per square metre) is the weight of one square metre of paper. In corrugated packaging it specifies each liner and the fluting medium — higher GSM means heavier, generally stronger paper, and it is one of the two figures (with BF) that define board quality.
GSM is a measure of substance, not of strength on its own. A 150 GSM kraft liner has more fibre per unit area than a 120 GSM liner, which usually means more strength, but the fibre quality matters just as much.
This is why Indian corrugated specifications almost always pair GSM with BF (burst factor). BF expresses the bursting strength relative to the paper's weight, so it captures fibre quality. A 150 GSM 20 BF paper and a 150 GSM 16 BF paper weigh the same and perform differently.
A full board specification therefore lists the GSM and BF of the outer liner, the medium and the inner liner. A typical 3-ply specification might read 150 GSM 18 BF outer / 120 GSM 16 BF medium / 150 GSM 18 BF inner.
When comparing quotes from different suppliers, this is where hidden cost differences usually sit. Two boxes described as "5-ply" can differ substantially in paper GSM and BF, and therefore in real strength and price.
GSM at a glance
| Unit | g/m² (grams per square metre) |
|---|---|
| Typical liner GSM | 120–250 GSM |
| Typical medium GSM | 100–150 GSM |
| Paired with | BF (burst factor) — indicates fibre quality |
| Spec format | Outer / medium / inner, each as GSM + BF |
Common questions
Does higher GSM always mean a stronger box?
Not necessarily. GSM measures weight per square metre, not fibre quality. A lower-GSM paper with a higher burst factor can outperform a heavier, poorer-quality one. Always compare GSM and BF together, plus the flute and ply.
What does "150 GSM 18 BF" mean?
It describes a paper weighing 150 grams per square metre with a burst factor of 18. GSM gives the substance and BF the strength relative to that weight, so together they define both how heavy and how strong the paper is.
Need Custom Corrugated Boxes for your product?
We manufacture custom corrugated boxes at our Rajkot unit and dispatch across India. Send the product, size or weight and monthly quantity and we specify and quote within one working day.
Or read the full specification: Custom Corrugated Boxes