Inch to Millimeter Converter
Length · unit-converter
Convert Inch to Millimeter with a fixed input and output unit, step-by-step formula line, and reference tables. All calculations use SI-based definitions (international yard, nautical mile, etc.).
Calculator
From: Inch (in)
To: Millimeter (mm)
About Inch
The inch is an imperial and US customary unit equal to exactly 0.0254 meters. Twelve inches equal one feet; it is used for screen sizes, tools, and fine measurements.
About Millimeter
The millimeter is a metric unit equal to one thousandth of a meter (0.001 m). It is used for precision engineering, 3D printing, and small tolerances.
How to convert inches to millimeters
1 inch is equal to 25.4 millimeter:
1 in = (0.0254 m ÷ 0.001 m) mm = 25.4 mm
Each inch is defined as 0.0254 m and each millimeter as 0.001 m, so one in equals 0.0254 ÷ 0.001 mm = 25.4 mm.
Let d(in) be the numeric value of the same length measured in Inch (in), and d(mm) the value in Millimeter (mm). Then:
d(mm) = d(in) × (0.0254 / 0.001)
Equivalently, divide by how many in fit into one mm (meters per mm divided by meters per in):
d(mm) = d(in) ÷ 0.03937007874016
Or: millimeter = inch ÷ 0.03937007874016
Examples
Example #1: Convert 20 in to millimeter
20 in = 20 in × (0.0254/0.001) mm = 508 mm
20 in = 20 in ÷ 0.03937007874016 = 508 mm
Example #2: Convert 50 in to millimeter
50 in = 50 in × (0.0254/0.001) mm = 1270 mm
50 in = 50 in ÷ 0.03937007874016 = 1270 mm
Summary
To convert Inch to Millimeter, multiply the value in in by the ratio of meters per in divided by meters per mm. Equivalently: value_mm = value_in × (0.0254 / 0.001). Numerically, 1 in equals 25.4 mm.
Relationship context
You are converting between US customary / imperial (Inches) and metric (SI) (Millimeters). Metric units are decimal; imperial units use inches, feet, yards, and miles tied to the international yard definition. Nautical miles are defined in meters (1 nmi = 1,852 m). This tool uses SI-based factors so results stay consistent with modern standards.
Conversion tables
| Inch (in) | Millimeter (mm) |
|---|---|
| 0.1 | 2.54 |
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 5 | 127 |
| 6 | 152.4 |
| 7 | 177.8 |
| 8 | 203.2 |
| 9 | 228.6 |
| Inch (in) | Millimeter (mm) |
|---|---|
| 10 | 254 |
| 20 | 508 |
| 30 | 762 |
| 40 | 1,016 |
| 50 | 1,270 |
| 60 | 1,524 |
| 70 | 1,778 |
| 80 | 2,032 |
| 90 | 2,286 |
| 100 | 2,540 |
Conversions outside the hub list
The grid on the category page lists hub units only. These pairs include at least one unit outside that hub set (same tools: formulas and tables on each page).
- inch to nmiInch to Nautical Mile
- inch to chainInch to Chain
- inch to fathomInch to Fathom
- inch to umInch to Micrometer
- inch to nmInch to Nanometer
- inch to angstromInch to Angstrom
- inch to pmInch to Picometer
- nmi to mmNautical Mile to Millimeter
- chain to mmChain to Millimeter
- fathom to mmFathom to Millimeter
- um to mmMicrometer to Millimeter
- nm to mmNanometer to Millimeter