Paper GSM to LB Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026Paper GSM to LB Calculator
Ordering paper from a supplier using a different weight system? This calculator converts GSM into the equivalent US pound basis weight for your paper category.
Basis Weight (lb) = GSM x Conversion Factor(by category)
Example
120 GSM text/book paper:
Basis Weight = 120 x 0.675 = ~81 lb (text/book)
Why the Same GSM Gives Different LB Numbers
GSM is a universal metric measure of paper density, but US pound basis weight is tied to the traditional uncut "parent sheet" size specific to each paper category - text/book, cover, bond, and index paper all use different reference sheet sizes, which is exactly why the same GSM converts to a different pound number for each.
Why This Confuses So Many People
A "65 lb cover" stock and an "80 lb text" stock can feel similarly thick and sturdy despite the very different pound numbers, precisely because they're measured against different reference sheet sizes - comparing GSM values (or converting both to the same category) is a more reliable way to compare true paper thickness.