Gsm means grams per square metre. It measures weight, not thickness or stiffness, though the three usually rise together. Two boards of the same grammage can feel different, so always judge a sample in the hand.
Typical ranges
| Folding cartons, light products | 300 to 350 gsm |
| Folding cartons, heavier products or large panels | 350 to 400 gsm |
| Rigid box wrap paper | 120 to 157 gsm art paper |
| Rigid box greyboard | 1,000 to 1,500 gsm, about 1.5 to 2.5 mm |
| Paper bags | 150 to 250 gsm, by size and load |
| Mailer boxes | E-flute corrugated, about 1.5 mm, described by flute rather than gsm |
What changes when you go heavier
- The box feels more solid and the panels bow less.
- Creases need more pressure, and may crack on dark solids unless the board is laminated.
- Unit price and freight weight both rise, roughly in line with the grammage.
Three common mistakes
- Choosing by number alone. A 350 gsm recycled board can be softer than a 300 gsm virgin board.
- Going heavy to protect a fragile product. An insert does that job better and for less.
- Forgetting the finish. Lamination adds stiffness, so a laminated 300 gsm carton often replaces an unlaminated 350.
If you are unsure, tell us the product weight and how the box will be handled. We send two plain samples in neighbouring weights so you can compare.