Enter a paper’s US basis weight (lb rating, such as “80 lb text” or “100 lb cover”) or its GSM, then select the paper category to convert between basis weight and grams per square meter (GSM).
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Paper Weight Conversion Formula
The following formulas convert a paper’s US basis weight (lb rating) to grams per square meter (GSM) for common paper categories (which use different US basis sheet sizes).
For Text / Book (25 × 38 in basis size):
Grams Per Square Meter = X * 1.481
For Cover (20 × 26 in basis size):
Grams Per Square Meter = X * 2.705
- Where X is the paper basis weight in pounds (lb rating for that category).
Paper Weight Conversion
What is the conversion of paperweight?
A paperweight conversion commonly refers to converting between the US basis weight system (paper “lb” ratings like 20 lb bond, 80 lb text, 100 lb cover) and GSM.
This is not a conversion from an arbitrary total weight of paper you have on a scale. In the US system, the “lb” rating is defined as the weight of 500 sheets at a specified basis sheet size (which varies by category), and that defined reference area is what makes the conversion to GSM possible.
Example Problem
How to perform a paper weight conversion?
First, determine the paper’s basis weight (lb rating) or its GSM.
For this example, the paper is rated as 40 lb text (basis weight).
Next, determine the paper category.
In this case, the paper is Text / Book.
Finally, calculate the GSM using the formula above:
Grams Per Square Meter = X * 1.481
Grams Per Square Meter = 40 * 1.481
Grams Per Square Meter = 59.24
FAQ
What is GSM in paper terms?
GSM stands for Grams per Square Meter and is a standard unit of measurement for the weight of paper. It indicates the quality and thickness of paper; the higher the GSM, the heavier and generally thicker the paper.
Why is paper weight conversion important?
Paper weight conversion is crucial for various industries, especially in printing and packaging, as it helps in determining the right type of paper for specific needs. It ensures compatibility with printing machines, affects postage costs, and influences the perception of quality in printed materials.
Can the same weight conversion formula be used for all types of paper?
No. In the US “basis weight” system, different paper categories use different basis sheet sizes (i.e., different reference areas for 500 sheets), so the lb↔GSM conversion factor depends on the category (for example, Text/Book vs Cover).
How does the weight of paper affect printing costs?
The weight of paper can significantly affect printing costs. Heavier paper (higher GSM) generally costs more to produce and can also increase postage costs for mailed items. However, it may be preferred for high-end prints due to its quality and durability.
