400×400

400×400 is a dimensional specification indicating 400 units in width and 400 units in height, forming a square. The symbol × often stands for multiplication but in this context denotes a size or resolution.

In mathematics and computer science, 400×400 commonly describes a 400-by-400 structure such as a matrix or grid. A 400×400 matrix has 160,000 elements. The term can also refer to a square image or region defined by 400 units per side, depending on the unit system used.

In digital imaging and design, 400×400 usually refers to pixel dimensions, written as 400 px by 400 px. A 400×400 image has an aspect ratio of 1:1 and is often used for thumbnails, avatars, or small icons. The file size depends on color depth and compression, so two images with the same dimensions can differ significantly in size.

Units beyond pixels are possible when the context specifies them, such as millimeters or inches. The physical size of a 400×400 square depends on the unit and, for digital measurements, on display density. For example, at 96 dots per inch, 400×400 pixels measure about 4.17 inches on each side (roughly 10.6 cm). At 300 dpi, the same pixels measure about 1.33 inches per side (about 3.39 cm).

In summary, 400×400 denotes a square dimension of 400 units per side, with the meaning adjusted by context to pixels, mathematical structures, or physical units.