Applies to: Grammage calculations and paper selection; thickness and feed compatibility require manufacturer specifications.
GSM means grams per square metre and describes grammage, not exact thickness or stiffness. Compare GSM within the context of paper type, then check the printer’s supported media weights and tray instructions before buying or feeding heavier stock.
GSM measures mass per unit area
Grammage expresses how many grams one square metre of the paper weighs. Because the value is based on area, it makes it easier to compare sheets of different finished sizes than traditional basis-weight labels alone.
A higher GSM usually means more material per area, but it does not uniquely determine thickness, stiffness, opacity, surface finish, or folding behavior. Fiber, coating, density, and manufacturing all matter.
Do not convert pounds without the paper category
North American basis weight states the mass of a ream measured at a category-specific basic sheet size. Bond, text, cover, and index stocks use different basic sizes, so the same pound number can describe very different papers.
A conversion table is only useful when it identifies the paper category. For purchasing, compare manufacturer specifications or physical samples rather than relying on a single approximate conversion.
Match paper to the printer path
Printer specifications usually list supported weight ranges by tray or media type. A device may accept heavy stock through a manual or rear feed while rejecting it from the main cassette or duplex path.
- Check the printer manual for supported GSM and media types.
- Use the recommended tray and feed direction.
- Select the matching Heavy, Cardstock, Labels, or similar setting.
- Fan ordinary paper only when the manufacturer recommends it.
- Print one sheet and inspect feed, curl, toner, or ink adhesion.
- Avoid automatic duplex if the stock exceeds that path’s limit.
Choose by the finished use
Everyday documents benefit from easy feeding and comfortable handling. Covers, menus, cards, and signs may need more stiffness or opacity, while folded pieces also need a grain direction and thickness that crease cleanly.
Request samples for a print job where feel, show-through, color, or folding matters. GSM narrows the choice, but a sample reveals the characteristics that a number cannot.
Calculate approximate sheet mass without confusing it with thickness
An A4 sheet has an area of 0.210 × 0.297 = 0.06237 square metres. At 80 g/m² its nominal mass is 4.9896 g, so 100 sheets are approximately 499 g before packaging or moisture variation. This arithmetic helps with an estimate, not a guaranteed shipping weight.
Two papers with the same GSM can differ in stiffness and thickness because of coatings, fiber and density. Check the printer’s range for the specific tray and duplex path, then test a supported sample. GSM alone is not permission to feed stock through every path.
Sources and further reading
Vendor instructions and background references are linked below. Worked examples are our explanatory calculations, not vendor performance claims. Check the instructions for your current software and device.
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