Exact inch to millimeter reference
Convert 1-1/4 inches to millimeters for CNC setup sheets, drawings, inspection notes, and supplier communication. The formula uses the exact international inch standard.
Answer first
1-1/4 inches =
31.7500 mm
The exact conversion uses 1 inch = 25.4 mm. This page displays 31.7500 mm by default. For CNC, inspection, RFQ, or supplier documents, keep the precision required by the drawing, tolerance block, process plan, or inspection equipment.
A 1-1/4 inch value often appears in legacy drawings and stock references. Convert first, then validate tolerance, fit, and actual material callout.
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.
1-1/4 inches equals 31.7500 mm using the exact conversion factor 1 inch = 25.4 mm.
Use mm = inch × 25.4. For this page, 1.25 × 25.4 = 31.7500 mm.
Use the precision required by the drawing, process plan, or inspection method. This page shows 31.75 mm, 31.750 mm, and 31.7500 mm so you can choose the appropriate display precision.
Yes. 1-1/4 inches is represented here as 1.25 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.
