GSM

GSM: Grams per square meter — the standard unit for measuring how heavy and thick playing-card paper is.

GSM (grams per square meter) is how the print industry talks about paper weight, and by proxy thickness, stiffness, and durability. Higher GSM generally means a thicker, stiffer, more durable card — but the relationship isn't linear, because how the paper is finished (calendered, coated, laminated to a black core) affects feel as much as raw weight. Playing-card stocks at Mr. Playing Card range from 280 GSM economy (light, fine for prototypes and short-lived promotional decks), through 300 GSM standard black-core (the default for real gameplay), 310 GSM premium linen and 310 GSM deluxe black-core (the magician and cardist favorites), up to waterproof 100% plastic for casino-grade and outdoor use. For context, premium consumer game decks like Bicycle Standard sit around 280–310 GSM. The two questions GSM answers in practice: 'Will this feel cheap?' (sub-280 GSM in a black-core construction can) and 'Will this last through hundreds of shuffles?' (310 GSM black-core absolutely will). GSM is also useful as a shorthand on quotes — when you ask a printer for '310 GSM linen black-core', you've specified weight, finish, and core construction in five words.