25.4
mm
2.54
cm
0.0254
m
25.4
mm
2.54
cm
0.0254
m
The Inches to Millimeters Converter converts inch values to millimeters with exact precision. The conversion factor is 1 inch = 25.4 mm (exact international definition). This converter is essential for precision manufacturing, CNC machining, 3D printing, and electronics where millimeter-level accuracy is required.
Converting inches to millimeters is a daily task in mechanical engineering, jewelry making, and medical device manufacturing. Millimeters provide a finer scale of measurement, and most international engineering drawings use metric dimensions.
Results are also provided in centimeters for convenience when working with larger dimensions.
The formula is exact: millimeters = inches × 25.4. For centimeters: cm = inches × 2.54. These conversions are mathematically exact because the inch is defined as precisely 25.4 mm.
Common reference points: 1/4 in = 6.35 mm, 1/2 in = 12.7 mm, 1 in = 25.4 mm, 12 in = 304.8 mm.
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Results
1/4 inch = 6.35 mm
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Results
12 inches = 304.8 mm
Exactly 25.4 mm. This is the international standard definition.
1/8 inch = 3.175 mm.
1/16 inch = 1.5875 mm.
Convert the fraction to decimal (e.g., 3/8 = 0.375), then multiply by 25.4. So 3/8 in = 9.525 mm.
1/4 in = 6.35 mm, 3/8 in = 9.525 mm, 1/2 in = 12.7 mm, 3/4 in = 19.05 mm.
In 1959, six countries formally agreed to define the inch as exactly 25.4 millimeters, replacing earlier slightly different definitions.
6 inches = 152.4 mm.
Yes, it is mathematically exact — not an approximation.
Many 3D printer models use metric measurements (mm). Design files from imperial-system users must be converted to mm for correct printing dimensions.
2 inches = 50.8 mm.
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