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Paper 101: The Difference Between Basis Weight vs. GSM

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SUMMARY:

  • Paper basis weight and GSM (grams per square meter) refer to the weight and thickness of paper, though basis weight is more common in North America and GSM is used on a more global scale.
  • Basis weight is more commonly used in paper for applications like business cards, brochures, and letterhead. 
  • GSM is used more frequently in associated with more specialty papers

There are a handful of paper terms or concepts that designers and graphic artists need to understand to help specify the right paper for their application. Basis weight and GSM (grams per square meter) are two such terms. 

Although both relate to the paper’s weight and thickness, they’re not interchangeable. Understanding the differences and when to use each term not only helps designers choose the right paper for their needs, but can also empower them to work more collaboratively with their printer — saving both time and money. Here, we’ll look at the difference between basis weight vs. GSM to help elevate your understanding of paper.  

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What is basis weight?

Basis weight is the standard measurement used in North America to describe weight in pounds, and is determined by dividing the weight of the ream (usually 500 sheets) by the standard sheet size (area) of that type of paper. It’s not a direct measure of thickness or density, but rather of the weight of paper in its raw form before any other factors like coating or finish are applied and it’s cut to its final dimensions.

“In addition to selecting a paper weight for the general feel of the design or target mailing weight, the paper basis weight you choose for your job is crucial to the color, image, and finishing quality,” write Elizabeth Gooding and Mary Schilling, authors of The Designer’s Guide to Inkjet, 3rd Edition. “The basis weight also has an impact on the opacity, with higher weight paper increasing the opacity of the sheet.”

Basis weight is typically used for papers that include text, such as cover papers, business cards, brochures, and letterhead, and it also applies when working with paper that traditionally uses this system — uncoated, offset, and certain specialty papers.

What is GSM?

Grams per square meter (GSM) is the metric system equivalent, which measures the actual weight and density of the sheet in grams for a one-square meter area. GSM doesn’t depend on the size or type of the paper, which means it can often provide a more accurate and consistent measure across different paper types.

Whereas basis weight is used for more traditional paper options, GSM is frequently used in association with more speciality papers.

“From a designer’s point of view, referring to and understanding GSM makes the most sense, as it refers to the actual weight of the sheet,” write Gooding and Schilling. “Other terms might be used based on the segment you’re designing for…but GSM is a standard term for basis weight that will apply across all segments.” 

Why understanding the differences between basis weight vs. GSM is important for designers 

Knowledge is power, and the more you know about each aspect of your project, the more you can get out of your time, energy, and budget. Understanding the differences between basis weight vs. GSM is important for:

Clear and consistent communication. There may be times you’re working with an international printer, in which case familiarities with both terms will be critical to avoid any confusion. Even working domestically, understanding the differences ensures everyone is (literally) on the same page so you can avoid costly mistakes. 

Paper thickness, feel, and durability. Both terms relate to thickness and sturdiness, but in different ways. Understanding how basis weight and GSM correspond ensures your printed materials have the look and feel you intend. For example, papers with a higher basis weight are often more durable and suited for projects like annual reports that need to withstand handling. 

Print production and compatibility. Not every printing press is optimized for every paper weight, which is why designers need to ensure the weight they choose is compatible with both the printer’s specifications and the print process they use.

Print quality. Ink is absorbed differently depending on different basis weights and GSM. While lighter papers may cause more ink absorption, leading to different textures or finishes, heavier papers often have a smoother surface, which can enhance the print quality.


“Porous offset papers lighter than 90 GSM may not be able to handle even a 240-percent maximum coverage,” write Gooding and Schilling. “Heavier and thick papers that are inkjet treated or inkjet coated may be able to handle a slightly higher TAC.” 

Cost management. One of the most essential parts of any project is ensuring you stay on budget without sacrificing the quality of your work. Heavier paper is more expensive, so a higher basis weight will increase not just the production costs of the print job, but also shipping costs — especially for bulk or direct mail campaigns.

 

“Sometimes a lower basis rate is chosen to cut costs…but if the paper weight selected was too low for the intended level of saturation or color coverage, problems such as show-through, paper mottle, cockle, and curl — as well as web breaks and finishing issues — may occur,” write Gooding and Schilling.

 
Understanding both basis weight and GSM gives designers the vocabulary they need to communicate every aspect of their project — from planning to printing and postage — and helps avoid both confusion and costly mistakes.
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The Designer’s Guide to Inkjet, 3rd Edition has everything you need to know about paper when designing for digital inkjet. Download the guide to learn more.