Exact inch to millimeter reference
Convert 1 inch to millimeters for CNC setup sheets, drawings, inspection notes, and supplier communication. The formula uses the exact international inch standard.
Answer first
1 inch =
25.4000 mm
The exact conversion uses 1 inch = 25.4 mm. This page displays 25.4000 mm by default. For CNC, inspection, RFQ, or supplier documents, keep the precision required by the drawing, tolerance block, process plan, or inspection equipment.
One inch is the anchor conversion for shop calculations. Use exactly 25.4 mm per inch, then apply any drawing tolerance or process allowance.
Reference-only caveat: this conversion does not certify tolerance, fit, pressure, load, code compliance, material equivalence, or interchangeability. Confirm the controlling drawing, standard, supplier data, and engineering approval before manufacturing.
1 inch equals 25.4000 mm using the exact conversion factor 1 inch = 25.4 mm.
Use mm = inch × 25.4. For this page, 1 × 25.4 = 25.4000 mm.
Use the precision required by the drawing, process plan, or inspection method. This page shows 25.40 mm, 25.400 mm, and 25.4000 mm so you can choose the appropriate display precision.
Yes. 1 inch is represented here as 1 inch before multiplying by 25.4 to get millimeters.
No. This is a reference unit conversion only. Confirm drawing tolerances, standards, material specifications, supplier certificates, and engineering approval before manufacturing or substituting parts.
