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To convert inches to millimeters, multiply by 25.4. So 0.5 inches = 12.7 mm, 1 inch = 25.4 mm, and 6 inches = 152.4 mm. Because the conversion is exact, the result is always a precise number — no approximation needed for the factor itself.
Plumbing and piping use a mix of both systems. A ½-inch pipe fitting is actually 12.7 mm in outer diameter. Metric pipe sizes like DN15 correspond to roughly the same bore. Engineers working on systems that combine US and international components constantly switch between inches and millimeters.
Did you know? The inch is subdivided differently in different industries: builders use 1/8-inch fractions, engineers use decimal inches (0.25"), and machinists use thousandths (0.001" = one "thou"). All of these translate cleanly to millimeters for international specifications.
Precision tool specifications — drill bits, end mills, gauge sizes — are listed in inches in US catalogs and millimeters in European ones. Pipe fittings, wire gauges, and PCB trace widths often need mm values for manufacturing. Furniture makers importing US plans convert imperial dimensions to mm for cutting on metric-calibrated tools.