Card stock, also called cover stock and pasteboard, is paper that is thicker and more durable than normal writing and printing paper, but thinner and more flexible than other forms of paperboard.
Other people, especially in the United States, describe paper in terms of pound weight—the weight in pounds per ream (500 sheets) of the paper with a given area (based on historical production sizes before trimming): for card stock, this is 20 by 26 in (508 by 660 mm); as compared to newsprint (thinner paper) of 24 by 36 in (610 by 914 mm).
In the United States, this usually is expressed in thousandths of an inch, often abbreviated thou points (pt.
The length and width of card stock often are stated in terms of the ISO system of paper sizes, in which specific dimensions are implied by numbers prefixed with the letter A.
Card stock labeled A3, for example, measures 420 × 297 mm (16.5 × 11.7 in).