Paper Weight Calculator
Why "20 lb Paper" and "24 lb Paper" Aren't Actually Comparable
Paper weight measured in pounds is one of the more confusing conventions in printing, because the pound figure refers to the weight of 500 sheets at that paper category's specific basic sheet size — a size that's different for bond, text, cover, index, and tag stock. That means 20 lb bond and 20 lb cover are not the same actual thickness at all. Grams per square meter (GSM) sidesteps the problem entirely by measuring weight per unit area directly, which is why it's the international standard. This calculator converts between the two using the correct factor for each paper category.
The Formula
GSM = lb × Conversion Factor
The conversion factor depends on paper category: 3.76 for bond/writing, 1.48 for text/book, 2.708 for cover, 1.622 for index, and 1.626 for tag — each reflecting that category's standard basic sheet size used to define the pound weight.
Where This Calculation Matters
- Cross-supplier comparisons — converting a supplier's lb spec to GSM to compare against a stock quoted in metric units.
- International ordering — specifying stock accurately for a print run going to a supplier that only quotes GSM.
- Matching an existing print — reproducing a document's paper feel by converting its known weight into the units your supplier uses.
- Print software and press settings — some digital presses and RIP software require GSM input regardless of how the stock was purchased.
Common Paper Weights Converted to GSM
| Paper | GSM equivalent |
|---|---|
| 20 lb Bond (standard copy paper) | 75.2 gsm |
| 24 lb Bond | 90.2 gsm |
| 60 lb Text | 88.8 gsm |
| 80 lb Text | 118.4 gsm |
| 65 lb Cover | 176.0 gsm |
| 80 lb Cover | 216.6 gsm |
| 100 lb Cover | 270.8 gsm |
| 110 lb Index | 178.4 gsm |
Figures above are computed from this calculator's own conversion factors for each paper category — always confirm exact GSM with your specific supplier, since basic sheet sizes can vary slightly by mill.
How to Use This Calculator
- Choose a direction: GSM → lb or lb → GSM.
- Select the paper type: Bond/Writing, Text/Book, Cover, Index, or Tag.
- Enter the known weight value.
- Select Calculate to get the converted weight.
Related Calculations
To confirm a card layout fits correctly on the stock you've chosen, see the Business Card Layout Calculator. For sizing bleed and safety margins on that same stock, use the Bleed and Margin Calculator.