Paper grammage (gsm)
How heavy a paper is, in grams per square meter. The number that decides whether your card feels flimsy or expensive.
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What it is
Grammage is the mass of one square meter of a sheet, written in gsm (or g/m2). It is the cleanest way to talk about how substantial paper feels, because it does not care about sheet size the way the American 'basis weight' in pounds does. Rough anchors: 80 to 100 gsm is office copy paper, 120 to 170 gsm is a decent flyer or magazine cover, 250 to 350 gsm is standard business card territory, and 400 gsm and up is the heavy 'this agency has money' card.
Use it whenever you brief a printer, because 'thick' means nothing and gsm means exactly one thing. Heavier stock also resists show-through, so double-sided pieces with dark backgrounds want more grammage than you think. Going heavier costs more in both paper and postage, and past roughly 170 gsm a sheet needs scoring before it will fold without cracking.
Gotcha: grammage is mass, not thickness. A bulky uncoated sheet and a dense coated sheet at the same gsm feel completely different in hand, because coating adds weight without adding bulk. If the physical thickness matters (card feel, box rigidity, spine width), spec caliper in microns or points alongside the gsm.
Ask AI for it
Spec the paper grammage for this piece and explain the tradeoff. Give the gsm value, state what it feels like in hand, and check it against the use case: folding (does it need scoring above 170 gsm), show-through on double-sided printing, mailing weight and postage bands, and cost. Where physical thickness matters, also give the expected caliper in microns and note that coated and uncoated sheets at the same gsm differ in bulk.