Paper 101: Understanding Basis Weight, GSM and Why it ...

When it comes to selecting the appropriate paper for your needs, the concept of basis weight is paramount. For anyone involved in the printing, packaging, or any other industry that utilizes paper, a clear grasp of basis weight can significantly enhance both the effectiveness and the economic viability of your projects. Typically, higher basis weight materials carry a higher price tag. A solid understanding of basis weight allows printers, designers, and manufacturers to make informed choices about which sheets to utilize, facilitating a balance between quality and cost in their respective projects.

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Understanding Basis Weight

What exactly is basis weight, and why does it matter? In straightforward terms, basis weight refers to the weight of a ream of paper (500 sheets) measured in its standard size. However, its significance extends far beyond sheer weight; basis weight can affect aspects such as durability, texture, and the manner in which inks and finishes are applied to the paper.

Defining Basic Sheet Size

The basic sheet size of paper is the original dimensions of the paper before any adjustments or cuts are made. It indicates the standard size of the sheet used to determine basis weight, which can vary depending on the type of paper. For instance, text and book paper typically have a basic sheet size of 25 x 38 inches, while cover paper has a basic size of 20 x 26 inches.

Grasping the concept of basic size is essential, as it directly influences the calculated basis weight of the paper being considered. For example, an 80# book paper will have a different thickness than an 80# cover paper. When comparing these grades, printers and designers often rely on GSM.

Understanding GSM

GSM (grams per square meter) is a universal standard for measuring paper density. It involves determining the weight of a square meter of paper, making it a useful metric for comparing the thickness and density of various types of paper, regardless of their specific size or basis weight.

The Purpose of a Basis Weight Conversion Chart

A basis weight conversion chart is invaluable for comparing weights across different paper types, enhancing your understanding of how one grade correlates to another. For instance, a 20# bond paper can be likened in thickness to a 50# text paper, with both approximately equating to a GSM of 75. Utilizing a conversion chart enables you to perform precise evaluations of these two paper types, aiding in more informed decisions during the selection process.

Be sure to download our Basis Weight Conversion Chart or check out our Paper Calculator for more information on GSM and additional paper-related measurements.

Common Paper Grades and Their Basic Sheet Sizes

Here’s a quick look at several standard paper grades and their common applications:

• 1. Bond/Writing Paper: Typically employed for letterheads, business forms, and stationery, with a basic sheet size of 17 x 22 inches.
  2. Text/Book Paper: Widely used for books, brochures, and catalogs, possessing a basic size of 25 x 38 inches.
  3. Cover Paper: A thicker, more durable paper used for book covers, reports, and presentations, with a basic sheet size of 20 x 26 inches.
  4. Bristol Paper: Known for its stiffness and smooth surface, suitable for greeting cards and postcards; its basic size is 22.5 x 28.5 inches.
  5. Index Paper: Ideal for index cards and file folders, with added stiffness, having a basic size of 25.5 x 30.5 inches.
  6. Tag Paper: Renowned for its robustness, often used for price tags and folders, with a basic size of 24 x 36 inches.