Inch to Millimeter Converter
Type a value — the answer appears instantly. 1 in = 25.4 mm.
Reviewed by the OmniCalc teamMethod verified 2026-07-01
25.4 millimeters
= 0.0254 m= 0.0833333 ft
equals 25.4 millimetersFormula: mm = in × 25.4
Inch to Millimeter formula
mm = in × 25.4
Convert 5 inches to millimeters
- Start with 5 inches.
- Multiply by the conversion factor: 5 × 25.4 = 127.
- So 5 in = 127 mm.
Inch to Millimeter conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 0.01 in | 0.254 mm |
| 0.1 in | 2.54 mm |
| 0.25 in | 6.35 mm |
| 0.5 in | 12.7 mm |
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 4 in | 101.6 mm |
| 5 in | 127 mm |
| 6 in | 152.4 mm |
| 7 in | 177.8 mm |
| 8 in | 203.2 mm |
| 9 in | 228.6 mm |
| 10 in | 254 mm |
| 15 in | 381 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 30 in | 762 mm |
| 40 in | 1,016 mm |
| 50 in | 1,270 mm |
| 75 in | 1,905 mm |
| 100 in | 2,540 mm |
| 250 in | 6,350 mm |
| 500 in | 12,700 mm |
| 1,000 in | 25,400 mm |
| 5,000 in | 127,000 mm |
| 10,000 in | 254,000 mm |
Unit definitions
What is a inch?
The inch is an imperial and US customary length unit defined as exactly 0.0254 metres since 1959. It is widely used in the United States and for screen sizes, pipe diameters, and lumber. Twelve inches make one foot.
What is a millimeter?
The millimetre is one thousandth of a metre, an SI unit of length. It is the finest gradation on most metric rulers and is standard for engineering drawings, machining tolerances, and rainfall measurement. Ten millimetres make one centimetre.
Frequently asked questions
How many millimeters are in one inch?
One inch equals 25.4 millimeters (1 in = 25.4 mm).
How do I convert inches to millimeters?
Multiply the value in inches by 25.4. For example, 10 in × 25.4 = 254 mm.
Which is bigger — a inch or a millimeter?
A inch is bigger: one inch contains 25.4 millimeters.
Is this inch to millimeter converter free?
Yes — the converter is free, works offline once loaded, and computes instantly in your browser without sending your numbers to a server.
Conversion factors follow international definitions (SI / NIST). Last verified 2026-07-01.