How many millimeters are in one inch?

One inch is defined as exactly 25.4 millimeters in the metric system. This relationship is established and used universally in conversions between imperial and metric measurement systems. The conversion factor is important for various applications, including welding print reading, where precision in measurements is critical. Understanding that one inch equals 25.4 millimeters allows welders and technicians to accurately interpret and convert dimensions on engineering drawings and specifications, which may be given in either metric or imperial units. This knowledge helps ensure that components fit together correctly and that welding specifications are met accurately.