PAPER CALCULATOR
Basis Sizes and Areas
Basis weight relates to how heavy any particular paper is. Here in the US, it's measured differently than the rest of the world.

In countries which rely on the metric system, the weight of paper is measured by the number of grams per square meter (g / m²). No matter what size paper or what intended application, there is simply one reference measurement.

In the US (and most of North America), however, things aren't so clear. Here, paper weights are measured according to the intended application - for example, you'll hear terms like "80 lb Cover" or '20 lb Bond". To make matters worse, an 80 lb Cover and an 80 lb Book (or text) don't weigh the same.

So what does the term basis weight mean? Simply put, the basis weight is the weight of 500 sheets of paper when cut to the basis size for that particular paper type. The basis size is the reference size for that paper type, and while at first this seems confusing, there's actually a logical reason behind it. Let's look at the basis sizes for the most common paper types:

 

Basis Sizes and Areas
Paper Type Basis Size Common Usages
Book / Offset 25" x 38" (635 x 965 mm) Text and trade books, magazines, direct mail, brochures and catalogs
Cover 20" x 26" (508 x 660 mm) Coated or uncoated magazines, books, catalogs and annual reports
Bond 17" x 22" (432 x 559 mm) Writing papers, copy paper, mimeo and business forms
Tag / Newsprint 24" x 36" (610 x 910 mm) Newspapers, low grade inserts or flyers
Bristol 22.5" x 28.5" (571 x 724 mm) Point of purchase (POP) materials, display advertising
Index 25.5" x 30.5" (648 x 775 mm) File cards, file folders, and jackets


 

There is a very pragmatic reason these basis sizes were chosen to represent a "standard" ream size - they are the most common sizes chosen to eliminate waste on a printing press. For example, the basis size for bond paper (writing paper) is 17 by 22 inches - which can be cut into four 8.5 × 11 inch sheets (or "letter size" paper). Similarly, the 25 in × 38 in book paper ream was developed because it can easily be cut into sixteen 6 in × 9 in book-sized sheets without significant waste. And early newsprint presses produced printed sheets 2 ft × 3 ft in size, and so the ream dimensions for newsprint became 24 in × 36 in.

We hope this introduction has helped you understand the way basis weights are determined in the US system. Now, please feel free to select one of our paper calculators by choosing a link above. Feel free to bookmark the links and use them at any time!