Quick answer: 1 Inch in Millimeter
1 in equals 25.4 mm. To convert Inch to Millimeter, multiply by 25.4 using the free calculator above — no signup needed.
Length units
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About Length Converter
The Length Converter converts between 12 different units, including Meter, Kilometer, Centimeter, Millimeter, Micrometer. The base unit is the Meter, and every other unit on this page is defined as an exact multiple of it. Type any value into the calculator above to convert instantly — free, unlimited, no signup and nothing to install.
Common equivalents: 1 Meter = 0.001 Kilometer, 100 Centimeter, 1000 Millimeter.
Scale of this category: the smallest unit is the Nanometer (nm) and the largest is the Light Year (ly).
Last updated: 2026-09-15
Length conversion factors
| Unit | Symbol | Value in Meter |
|---|---|---|
| Meter | m | 1 m = 1 m |
| Kilometer | km | 1 km = 1000 m |
| Centimeter | cm | 1 cm = 0.01 m |
| Millimeter | mm | 1 mm = 0.001 m |
| Micrometer | µm | 1 µm = 0.000001 m |
| Nanometer | nm | 1 nm = 0.000000001 m |
| Mile | mi | 1 mi = 1609.34 m |
| Yard | yd | 1 yd = 0.9144 m |
| Foot / Feet | ft | 1 ft = 0.3048 m |
| Inch | in | 1 in = 0.0254 m |
| Nautical Mile | nmi | 1 nmi = 1852 m |
| Light Year | ly | 1 ly = 9460730472580800 m |
Worked Examples
See exactly how the conversion works with real numbers, step by step.
How much is 1 Inch in Millimeter?
- Multiply 1 by the conversion factor 25.4
- 1 Inch = 25.4 Millimeter
How much is 5 Inch in Millimeter?
- Multiply 5 by the conversion factor 25.4
- 5 Inch = 127 Millimeter
How much is 25 Inch in Millimeter?
- Multiply 25 by the conversion factor 25.4
- 25 Inch = 635 Millimeter
Quick Conversion Reference Table
| Inch (in) | Millimeter (mm) |
|---|---|
| 1 in (Inch) | 25.4 mm (Millimeter) |
| 2 in (Inch) | 50.8 mm (Millimeter) |
| 5 in (Inch) | 127 mm (Millimeter) |
| 10 in (Inch) | 254 mm (Millimeter) |
| 20 in (Inch) | 508 mm (Millimeter) |
| 50 in (Inch) | 1270 mm (Millimeter) |
| 100 in (Inch) | 2540 mm (Millimeter) |
| 500 in (Inch) | 12700 mm (Millimeter) |
| 1000 in (Inch) | 25400 mm (Millimeter) |
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How to Use This Converter
- Enter your value
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FAQ
How much is 1 Inch in Millimeter?
1 Inch = 25.4 Millimeter.
How do I convert Inch to Millimeter?
Enter your value in Inch into the converter above and the result in Millimeter appears instantly. 1 in equals 25.4 mm — just multiply your value by 25.4.
What is the formula for Inch to Millimeter?
The formula is: value in Millimeter = value in Inch × 25.4. For example, 5 in × 25.4 = 127 mm.
Is this Inch to Millimeter converter free and accurate?
Yes. This Inch to Millimeter converter is 100% free, uses the exact international conversion factor (25.4), and works on any device with no signup.
How do I convert Millimeter back to Inch?
To convert back, divide by 25.4 (or multiply by 0.0393701). You can also use our dedicated How Many Inch in 1 Millimeter? page for instant results.
Do I need to download an app or sign up?
No. The converter runs entirely in your browser — nothing to install, no account, no fees. It even keeps working offline once the page has loaded.
Which Length units are supported?
This converter supports 12 units: Meter, Kilometer, Centimeter, Millimeter, Micrometer, Nanometer, Mile, Yard, Foot / Feet, Inch, Nautical Mile, Light Year.