4×5

4×5 is a notation that can refer to either a multiplication or the dimensions of an object. In mathematics, 4×5 denotes the product of 4 and 5, equal to 20. When used as a dimension, 4×5 describes a rectangle with sides measuring 4 by 5 units.

In geometry, a 4 by 5 rectangle has an area of 20 square units and a perimeter of 18 units. A grid of 4 rows by 5 columns contains 20 individual cells. The expression is commonly used to convey size in plans, diagrams, and layouts.

In photography and printing, 4×5 refers to a sheet film size of four inches by five inches, a standard format in large-format systems. The film was widely used with view and field cameras, delivering high image resolution due to its large negative area. In metric terms, this format is 10.16 cm by 12.7 cm, covering about 129 cm².

The term also appears in print and display contexts to denote corresponding paper or print sizes; some cameras and accessories are designed specifically to work with 4×5 sheets, such as film holders and reducing backs. The format remains notable in photography history for its balance of portability and image detail.