how big is an index card

An index card typically comes in several common sizes, with the most standard and widely used size being 3 inches by 5 inches (3" x 5") or 7.62 cm by 12.7 cm. Other popular sizes include 4" x 6" (10.16 cm by 15.24 cm) and 5" x 8" (12.7 cm by 20.32 cm). These cards are made of card stock and can be blank, ruled, or grid-lined depending on their intended use.