Printing Terminology: What does GSM mean in regard to Paper?

estimated reading time: 4 minutes

What does GSM stand for?

GSM stands for Grams per Square Meter. It is a standardized method for expressing the weight of paper. Abbreviated as GSM or gsm, it represents the weight in grams of a single sheet of paper measuring one square meter (e.g. one meter in width by one meter in length).

Paper Weight: Metric System vs Imperial System

Most countries of the world use the metric system for expressing weights and measures. As such, the GSM system, which uses the metric units of grams and meters, is the international standard and the most widely used method for expressing the weight of paper.

However, in the United States, Imperial measurements (such as pounds and inches) are still widely used for expressing weights and measures. Hence, the predominant US system for designating the weight of paper is not GSM. Though the use of GSM is gradually becoming more commonplace in the US, the weight of paper is still expressed as "Pounds" the majority of the time (with Pounds usually being abbreviated as lb or #).

The pound weights are derived from the weight of 500 sheets of a given paper in its Basic size. These Basic sizes are designated using Inch increments and vary by paper category.

The Basic sizes of common paper categories are shown below…

Bond Paper: 17" x 22"
Book, Text, and Offset Papers: 25" x 38"
Cover Paper: 20" x 26"
Index Paper: 25.5" x 30.5"

Here are some examples of how the pound designation for paper stocks is determined. If 500 sheets of Bond paper in its Basic Size of 17" x 22" weigh a total of 20 pounds, the paper is labelled as 20# Bond. If 500 sheets of Offset paper in its Basic Size of 25" x 38" weigh a total of 60 pounds, the paper is labelled as 60# Offset. Likewise, if 500 sheets of Cover paper in its Basic Size of 20" x 26" weigh a total of 100 pounds, the paper is labeled as 100# Cover.

This system of Basic sizes can be confusing because each category of paper has a different Basic size. For example, 24# Bond paper is actually heavier than 50# Offset paper. So you can't always go by the # designation when comparing two different categories of paper because the Basic sizes are different. However, within the same paper category a larger pound designation will always signify a heavier stock.

Compared to the # designation, the GSM system makes it instantly clear which stocks are heavier or lighter relative to other stocks. This is because instead of having a different Basic size for each category of paper, the GSM system uses a consistent measurement of one square meter for all categories of paper. Hence, the higher the GSM, the heavier the paper…and the lower the GSM, the lighter the paper.

Does GSM designate a Paper's Thickness?

Not exactly. It is a common misconception that GSM designates a paper's thickness. GSM only designates the weight of the paper, not its measurable thickness. However, GSM ratings will provide a relative thickness when comparing two stocks within the exact same paper category. In this case, the stock with the higher GSM will be thicker than the stock with the lower GSM.

The same holds true for the "Pounds" designation of paper. The Pound rating does not provide the thickness of the paper, only its weight. However, just like with the GSM system, the Pounds can provide a relative thickness when comparing two stocks with the same paper category. In this case, the higher the pound rating, the thicker the stock.

Whether using the GSM system or the Pounds system, the physical thickness of a paper stock can be measured with a caliper, paper gauge, or other precision measuring device. Also, most paper manufacturers publish online charts that show nominal thicknesses for the various paper types. These thicknesses are usually shown in microns, millimeters, and/or increments of an inch.

In addition, thicker paper stocks and cardstocks are often designated using Points. One point, often abbreviated as "PT", is equal to 1/1000th of an inch (.001"). Hence, a 12PT cardstock would be .012" in thickness. A 14PT cardstock would be .014" in thickness, and so on.

Color Vision is always ready to help!

As a full-service printer, Color Vision can assist with just about any printing need you may have. Plus, we're always happy to help you choose the right type and weight of paper for your projects.

So whether you are looking for book printing, full color printing, laminated printing or something else, be sure to give us a call at 800-543-6299 to discuss your printing needs.

Or, use our simple Quote Request form to send us your project's specifications and we will email a custom quote to you.

As always, we look forward to assisting with your next print project!

Related Article: The meaning of Paper Basis Weight