100mm

100 millimeters (100 mm) is a unit of length in the metric system. It equals one tenth of a meter and ten centimeters, and is approximately 3.94 inches.

Used across science, engineering, and industry, 100 mm is a common nominal size for components and features. In technical drawings, dimensions are often specified in millimeters, with 100 mm representing a straightforward, whole-number measurement. This size appears in applications such as pipe diameters, fastener lengths, machining tolerances, and packaging dimensions.

In photography and optics, 100 mm denotes a focal length. A 100 mm lens provides a moderate telephoto perspective and is commonly used for portrait work on full-frame cameras. There are also 100 mm macro lenses designed for close-up photography, offering magnification suitable for small subjects.

The prevalence of the metric system means 100 mm is an unambiguous, internationally understood unit for describing length. It facilitates precise communication across disciplines, from engineering and construction to manufacturing and scientific research.