Card stock (also called cover stock or pasteboard) is a paper stock that is thicker and more durable than normal writing or printing paper, but thinner and more flexible than other forms of paperboard. Card stock is often used for postcards, playing cards, catalog covers, scrapbooking, and other uses which require higher durability than regular paper. The texture is usually smooth, but can be textured, metallic, or glossy.

Card stock thickness is often described by pound weight. Pound weight is the weight of 500, 20" by 26" sheets. This differs from how text stock is determined, which assumes 500, 25" by 38" sheets. Most countries use the term grammage to describe the weight of the paper in grams per square meter. The term card stock is used to describe paper with weights from 50lb to 110lb (about 135 to 300 g/m²).

In the US, card stock thickness is usually measured in points or mils that gives the thickness of the sheet in thousandths of an inch. For example, a 10 pt. card is 0.010 inches (0.25 mm) thick (roughly corresponding to a weight of 250 g/m2); 12 pt. is 0.012".