Kraft Paper Bag Grammage and Ply: A Buyer’s Guide

A kraft paper bag is built from one or more layers (“plies”) of paper. The ply count and the grammage (GSM) of each layer decide how strong, how stiff and how expensive the bag is.

Reading the construction code

• 2-ply (2P) — two layers of kraft; lightweight and economical for firm, non-abrasive contents.
• 3-ply (3P) — three layers for heavier, sharper or more demanding loads.
• 2-ply one-film (2P1F) / 3-ply one-film (3P1F) — one of the plies is a film liner that adds moisture protection and reduces powder leakage.

Grammage (GSM)

Grammage is the weight of one square metre of paper. Higher GSM means stronger, stiffer paper but more weight and cost. For valve bags, the typical range is roughly 70–90 g/m² per ply, tuned so the bag is strong enough to fill, stack and ship without being unnecessarily heavy.

How to choose

• Light, non-abrasive fills — 2-ply with moderate GSM is usually enough.
• Heavy, sharp or dusty fills — go 3-ply and consider a film liner.
• Humidity or leakage concern — add one film ply for the barrier.

We build 2P, 3P, 2P1F and 3P1F valve bags with width 35–48 cm, length from 37.5 cm and a 10.5 cm valve. Tell us your product weight and handling, and we will recommend a construction.