Paper Weight & GSM Calculator
Convert between pounds and grams per square metre for bond, text, cover, index, and watercolor paper stocks, and get a recommended gsm range for the medium you're drawing with.
Converted weight
Recommended paper weight
Smooth or lightly toothed cartridge paper — heavy enough to erase and layer graphite without pilling.
Why lb and gsm don't line up 1:1
Grams per square metre is a true area-based measurement, so 200gsm always means the same physical weight of paper. The US "lb" system instead measures 500 sheets of a category's historical parent sheet size before it's cut down — so the conversion factor from lb to gsm depends on which basis (bond, text, cover, index, or watercolor) the number belongs to. This tool derives each conversion factor from its basis sheet size (the grams in a pound over the area of 500 basis sheets) and converts either direction.
When in doubt, gsm is the more reliable spec to shop by, since it doesn't depend on knowing which basis a supplier is quoting.
Frequently Asked Questions
Why does 24lb paper convert to a different gsm than 24lb cover stock?
A US "lb" weight is a basis weight: the weight of 500 sheets at that paper category's standard, uncut parent sheet size. Bond/writing paper is measured on a 17×22in parent sheet, text/book paper on 25×38in, cover on 20×26in, index on 25.5×30.5in, and watercolor paper on 22×30in (which is why 140lb watercolor paper is about 300gsm). Because the parent sheets differ, the same lb number means a physically different sheet weight across categories — gsm (grams per square metre) is the fairer, size-independent comparison.
What gsm is a typical sketchbook?
Most everyday cartridge sketchbooks run 90–160gsm — light enough to fill quickly but heavy enough to erase and layer graphite without pilling or tearing. Mixed-media and watercolor-pencil pads jump much higher, commonly 300gsm and up, because wet techniques need a heavier, sized sheet to resist buckling.
Do I need heavier paper for ink than for pencil?
Usually yes, if any wash or wet blending is involved. Dry graphite and dry colored pencil work fine on a lighter 90–160gsm sheet. A fineliner with even a light water wash benefits from 160–224gsm smooth or hot-press stock so the ink doesn't feather or the sheet doesn't cockle.
What's the difference between cold-press and hot-press for watercolor pencil?
That's texture, not weight, but the two often go together: cold-press sheets have a pronounced tooth that grips pigment and blends well with a wet brush, while hot-press is smoother and better suited to fine detail. Either way, look for 300gsm (140lb) or heavier if you plan to wet-blend, so the sheet doesn't warp.
Educational tool only. Basis-weight conversion factors are industry-standard approximations; always check a specific paper's printed gsm or lb rating against the manufacturer's own spec sheet before buying in bulk.