210mm

210 millimeters (210 mm) is a unit of length in the metric system. It is equal to 0.21 meters or about 8.27 inches. The prefix milli- denotes one thousandth, so 210 mm represents 210 thousandths of a meter.

In everyday use, 210 mm is most commonly encountered as a dimension: the width of standard ISO A-series paper, including A4, which has a width of 210 mm. ISO 216 defines these sizes and keeps the same aspect ratio when moving to other sizes (A0, A1, etc.).

In technical and industrial contexts, 210 mm can describe the bore diameter of firearms and large-caliber artillery, where bore diameter is stated in millimeters. It can also appear as a nominal diameter in piping and other components.

Conversions: 210 mm equals 21 cm, 0.21 m, and approximately 8.27 inches.

See also: Millimetre; Metre; A-series paper; Caliber (ordnance).