Basis weight of paper

Basis weight (commonly known as "gram weight") is the most fundamental and core indicator in the physical performance system of paper. It is defined as the standard weight of paper per unit area, and the general measurement standard is "grams per square meter (g/m²)", that is, the constant weight value of paper per square meter under standard temperature and humidity conditions (23℃±1℃, relative humidity 50%±2%).

In industry classification standards, basis weight is the key boundary to distinguish "paper" from "paperboard (board paper)" : Generally, categories with a basis weight of ≤250 grams per square meter are defined as paper, covering mainstream sub-sectors such as cultural paper, packaging paper, and special functional paper. Those with a basis weight greater than 250 grams per square meter are classified as cardboard (board paper), and are mostly used in scenarios with high requirements for stiffness and load-bearing capacity, such as heavy-duty packaging, base materials for cartons, and hardcover covers.

As the "fundamental anchor point" of paper performance, the level and uniformity of basis weight directly determine the core characteristics and application adaptability of the paper: the higher the basis weight, the stronger the thickness, stiffness and tear strength of the paper are usually, making it suitable for scenarios that require load-bearing, wear resistance or multiple folds. The lower the basis weight, the thinner and more flexible the paper will be, making it suitable for high-speed printing, continuous binding and other requirements. The uniformity of quantification (i.e., the fluctuation range of the weight per sheet and the entire batch of paper) is even more crucial - if the weight distribution is uneven, it will lead to inconsistent ink absorption of the paper, color deviation in printing, and even problems such as uneven force and dimensional deformation in post-processing stages like die-cutting and folding, directly affecting the quality stability of the final product.