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Basis Weight vs. Thickness: What Do These Paper Measurements Mean?

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The paper world is full of terms and concepts that sound similar but actually have different meanings. For example, understanding the difference between paper brightness and whiteness can significantly impact your choice of paper for a specific print project, and a misunderstanding of the difference could compromise the quality or performance of the piece. 

The trouble with basis weight vs. thickness as paper measurements is that these terms are often thought to be two sides of the same coin. But even though these types of measurements help designers and printers ensure their chosen paper stock can handle the print specs of a specific job, a paper can be produced with the same weight and be compressed into a thicker or thinner sheet.  

Here, we’ll break down basis weight vs. thickness to help you better understand what these two types of paper measurements mean, and how they can help you choose the right paper stock for your next project.

What is a paper's basis weight?

A paper’s basis weight is calculated by dividing the weight of a ream (500 sheets) by the standard sheet size (area) of a specific type of paper. Because sheet size for different types of paper can vary significantly, dividing the same weight by a different actual sheet size will produce a very different measurement. 

What’s more, because the base size is not the same for all different types of paper, basis weight should not be used as a 1:1 comparison between different paper types. For example, 80 lb. Text would actually be lighter than 80 lb. Cover due to the difference in the base size of the sheets. 

Basis weight can play a large role in the overall performance of the sheet, and it can also impact the choices a designer makes, particularly in terms of ink coverage and saturation. For print applications that require high degrees of color saturation and coverage, choosing a sheet with a lower basis weight can result in a number of print defects, including show-through, paper mottle, cockle and curl. 

What’s more, choosing a paper with a less-than-ideal basis weight can also hamper your ability to effectively utilize certain finishing techniques. 

Another component worth mentioning in the discussion of a paper’s basis weight is grams per square meter (gsm), which is a counterpart to basis weight in measuring how heavy a particular sheet is. The difference is that gsm refers to the actual weight of a particular sheet regardless of the paper type, and this simplified approach to calculating weight can make it easier and faster for designers to specify the right paper for their design or project.

What is a paper's thickness?

A paper’s thickness — also known as a sheet’s caliper — is represented in PPI (pages per inch) and measures the number of sheets that are in a one-inch stack of paper. The lower the number, the thicker the sheet. 

PPI and gsm will usually correlate, as a paper with a higher gsm will most often be a thicker stock. And given that gsm is a measurement of weight, a paper with a higher gsm will generally also have a higher basis weight, even if these two measurements are not an exact equivalent. 

However, you can find papers with the same PPI that do not have the same gsm. These papers use a unique engineering that provides a thicker feel without adding any additional weight, which can be useful in designing high-value direct mail pieces that don’t increase your postage from the added weight of a heavier paper stock. 

A paper’s PPI is particularly important when designing print that will go through a binding process. Thicker papers — or those with a lower PPI — can be less compatible with certain types of binding, particularly perfect binding, which is a key player in the book publishing industry. 

PPI is also important to account for when designing print projects like traditional direct mail postcards or self-mailers, as these pieces may need a higher-PPI paper to be compatible with USPS® sorting requirements. 

Understanding the difference between paper basis weight and thickness can go a long way in helping to ensure your design is reproduced accurately on the page, and that your project demonstrates a high level of quality and performance. Accent® Opaque offers a wide range of premium paper options to help you bring your designs to life.

Browse our Accent Opaque Text and Cover papers, and make sure to browse The Heavyweights, our new line of heavyweight paper available in weights of up to 130 lb.