Paper Weight Calculator

Understanding paper weight can be confusing because two different systems are used: GSM (Grams per Square Meter) and Basis Weight (lbs). Our Paper Weight Converter helps you easily switch between these systems to choose the right paper for your project.

What is GSM?

GSM stands for Grams per Square Meter. It is a universal and straightforward measurement. It represents the weight of one square meter of paper, regardless of the sheet size. A higher GSM means a heavier and typically thicker, more durable paper.

• 35-55 GSM: Very thin paper, like newsprint.
• 75-90 GSM: Standard office printer paper (e.g., 20 lb Bond is about 75 GSM).
• 120-140 GSM: Good quality paper for posters and flyers.
• 210-300 GSM: Cardstock, suitable for business cards, invitations, and book covers.
• 350+ GSM: Heavy cardstock, often used for premium business cards and packaging.

What is Basis Weight (lbs)?

Basis Weight, measured in pounds (lbs), is the more complex system, primarily used in North America. It is defined as the weight of a ream (500 sheets) of paper at its standard, uncut "basis size."

The confusion arises because the "basis size" is different for different types of paper. This means that a 80 lb "Text" paper is not the same thickness or sturdiness as an 80 lb "Cover" paper.

Here are the standard basis sizes used in our calculator:

• Bond: 17 x 22 inches (used for office paper)
• Text: 25 x 38 inches (used for commercial printing, books)
• Cover: 20 x 26 inches (used for cardstock, book covers)
• Index: 25.5 x 30.5 inches (used for index cards)
• Tag: 24 x 36 inches (used for tags and durable items)

How the Conversion Works

The conversion between GSM and Basis Weight is not a simple multiplication. It depends on the paper type's basis size. The formula used is:

GSM = (Basis Weight in lbs × 1406.5) / (Basis Size Area in square inches)

Our calculator automates this process. When you enter a poundage and select its type (e.g., 20 lb Bond), it first calculates the equivalent GSM. Then, it uses that GSM value to calculate what the equivalent poundage would be for all other paper types.

Practical Example

Let's say you have a 24 lb Bond paper. You enter "24" and select "Bond" as the type. The calculator determines this is equivalent to 90 GSM.

With that 90 GSM value, it then shows you the equivalents:

• It's like a 60 lb Text paper.
• Or a 34 lb Cover paper.

This shows that a "60 lb Text" paper is actually the same weight and density as a "24 lb Bond" paper, even though the pound numbers are very different.

Frequently Asked Questions (FAQ)

Why is GSM a better measurement?

GSM is a direct measure of weight per area, so it's a consistent, universal standard. A 100 GSM paper is 100 GSM everywhere, for any paper type. Basis Weight (lbs) is relative to the paper's category, which can be misleading if you're not familiar with the different basis sizes.

Is heavier paper always thicker?

Generally, yes. Higher weight (either GSM or lbs within the same category) usually corresponds to greater thickness (caliper). However, factors like material composition and finish can also affect thickness. For thickness measurements, you need a caliper or our Paper Thickness Calculator.

What is "20 lb paper"?

This almost always refers to "20 lb Bond" paper, which is the standard for everyday office and copy paper. It has a GSM of about 75.

How do I choose paper for my printer?

Most home and office printers work well with paper between 75 GSM and 120 GSM (approx. 20-32 lb Bond). For cardstock, check your printer's manual for its maximum supported paper weight, usually specified in GSM or Cover lbs.