Convert paper basis weight and GSM for text/book or cover paper to find the missing value using lb or kg inputs and paper category.
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Paper Weight Conversion Formula
The paper weight conversion calculator converts between US basis weight and GSM. Basis weight depends on the paper category because each category uses a different standard sheet size.
Convert basis weight in pounds to GSM:
Convert GSM to basis weight in pounds:
Convert basis weight in kilograms to pounds before calculating GSM:
Convert calculated basis weight in pounds to kilograms:
- GSM = grams per square meter
- BW_lb = basis weight in pounds
- BW_kg = basis weight in kilograms
- F = category conversion factor, in GSM per pound of basis weight
- 2.20462 = pounds per kilogram
If you enter a basis weight, the calculator converts it to pounds if needed, then multiplies by the selected paper category factor to find GSM.
If you enter GSM, the calculator divides by the selected paper category factor to find the basis weight in pounds. If you selected kilograms, it then converts the result from pounds to kilograms.
Paper Category Conversion Factors
The selected paper category changes the conversion because US basis weight is based on a ream of paper at a category-specific parent sheet size.
| Paper category | US basis size | Factor used | Formula to GSM |
|---|---|---|---|
| Text / Book | 25 × 38 in | 1.481 | GSM = lb × 1.481 |
| Cover | 20 × 26 in | 2.705 | GSM = lb × 2.705 |
Common Paper Weight Comparisons
| Basis weight | Text / Book GSM | Cover GSM |
|---|---|---|
| 60 lb | 88.86 GSM | 162.30 GSM |
| 80 lb | 118.48 GSM | 216.40 GSM |
| 100 lb | 148.10 GSM | 270.50 GSM |
Paper Weight Conversion Examples
Example 1: Convert 80 lb text paper to GSM
You select Text / Book, which uses a factor of 1.481.
So, 80 lb text paper is 118.48 GSM.
Example 2: Convert 270.5 GSM cover paper to basis weight
You select Cover, which uses a factor of 2.705.
So, 270.5 GSM cover paper is 100 lb cover.
Paper Weight Conversion FAQ
Why does the same pound weight give different GSM values?
US basis weight is not based on one universal sheet size. Text paper and cover paper use different parent sheet sizes. Because of that, 80 lb text and 80 lb cover are not the same thickness or mass per area. GSM is based on one square meter, so it is easier to compare across paper types.
What is the difference between basis weight and GSM?
Basis weight is the weight of a standard ream of paper in a specific category, usually stated in pounds in the US. GSM means grams per square meter. GSM measures weight per area, so it is more direct for comparing paper across categories.
Can you compare text weight directly to cover weight?
Not by the pound number alone. You should convert both to GSM first. For example, 80 lb text is about 118.48 GSM, while 80 lb cover is about 216.40 GSM. The cover stock is much heavier per square meter.
