Inches to millimeters Converter

Enter the inches, then press Calculate. The millimeters stay hidden while you type.

Press Calculate after the entries are in.

What this length conversion is for

Use this page when a measurement is written in inches and the next step needs millimeters. The number stays blank until you press Calculate, so a half-typed entry is never mistaken for the answer.

The factor

Multiply by the factor: 1 inch = 25.4 millimeters.

A worked example

12 inches are 304.8 millimeters. Multiply the result by the reverse factor if you want the original number back.

How to check it

Write the factor down, do the multiply on paper, and compare it with the result card. If you change a sentence on this page, edit the HTML file and reload. The form and this note live in the same file.

The reverse conversion is millimeters to inches. A nearby pair in the same units is inches to micrometers. When the converted number is the input to a job, continue with the height in inches and centimeters.