The most common size for an index card in North America and the UK is 3 by 5 inches (76.2 by 127.0 mm), which is also known as a 3-by-5 card. The second most popular size is 4 by 6 inches (101.6 by 152.4 mm) . Other sizes include 5 by 8 inches (127.0 by 203.2 mm) and ISO-size A7 (74 by 105 mm or 2.9 by 4.1 in) . The size of an index card can vary depending on the intended use, and they can come in a variety of colors and ruled or blank styles. Some index cards are even smaller, such as the mini 3" x 2.5" format, which is half the size of standard cards.