Inches to MM Converter
Inches to MM Converter
Enter a value and get an instant conversion.
Inches to MM Converter
Use our free Inches to MM Converter to quickly convert inches (in) to millimeters (mm). Enter any value in inches and get the equivalent measurement in millimeters instantly.
The conversion is exact because 1 inch equals exactly 25.4 millimeters.
Whether you are working with measurements, product dimensions, engineering specifications, hardware sizes, screen dimensions, or everyday measurements, this converter makes inches to millimeters conversion quick and easy.
How to Convert Inches to MM
The formula for converting inches to millimeters is:
Millimeters = Inches × 25.4
Since:
1 inch = 25.4 mm
you simply multiply the number of inches by 25.4.
Example: Convert 5 Inches to MM
To convert 5 inches to millimeters:
5 × 25.4 = 127 mm
Therefore:
5 inches = 127 mm
Example: Convert 10 Inches to MM
10 × 25.4 = 254 mm
Therefore:
10 inches = 254 mm
This same formula works for whole numbers, decimals, and fractional inch measurements after converting the fraction to a decimal.
Inches to MM Conversion Formula
The standard formula is:
mm = inches × 25.4
For example:
- 1 inch = 25.4 mm
- 2 inches = 50.8 mm
- 3 inches = 76.2 mm
- 5 inches = 127 mm
- 10 inches = 254 mm
The internationally standardized relationship is 1 inch = 25.4 millimeters.
Inches to MM Conversion Chart
| Inches (in) | Millimeters (mm) |
|---|---|
| 0.1 in | 2.54 mm |
| 0.25 in | 6.35 mm |
| 0.5 in | 12.7 mm |
| 0.75 in | 19.05 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 |
| 8 in | 203.2 mm |
| 10 in | 254 mm |
| 12 in | 304.8 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 |
| 100 in | 2,540 mm |
For a more extensive reference, the converter above can be used for any value. Common online references likewise use the exact 25.4 factor for these conversions.
Common Inches to MM Conversions
Here are some frequently searched values:
1 inch to mm:
1 in = 25.4 mm
2 inches to mm:
2 in = 50.8 mm
3 inches to mm:
3 in = 76.2 mm
4 inches to mm:
4 in = 101.6 mm
5 inches to mm:
5 in = 127 mm
6 inches to mm:
6 in = 152.4 mm
8 inches to mm:
8 in = 203.2 mm
10 inches to mm:
10 in = 254 mm
12 inches to mm:
12 in = 304.8 mm
20 inches to mm:
20 in = 508 mm
25 inches to mm:
25 in = 635 mm
50 inches to mm:
50 in = 1,270 mm
100 inches to mm:
100 in = 2,540 mm
Fractional Inches to Millimeters
Inches are often written as fractions, especially for hardware, construction and mechanical measurements. Convert the fraction to a decimal first, then multiply by 25.4.
| Inches | Decimal Inches | Millimeters |
|---|---|---|
| 1/16 in | 0.0625 | 1.5875 mm |
| 1/8 in | 0.125 | 3.175 mm |
| 3/16 in | 0.1875 | 4.7625 mm |
| 1/4 in | 0.25 | 6.35 mm |
| 5/16 in | 0.3125 | 7.9375 mm |
| 3/8 in | 0.375 | 9.525 mm |
| 1/2 in | 0.5 | 12.7 mm |
| 5/8 in | 0.625 | 15.875 mm |
| 3/4 in | 0.75 | 19.05 mm |
| 7/8 in | 0.875 | 22.225 mm |
| 1 in | 1 | 25.4 mm |
Example: Convert 3/8 Inch to MM
First convert:
3/8 = 0.375 inches
Then:
0.375 × 25.4 = 9.525 mm
Therefore:
3/8 inch = 9.525 mm
Inches vs Millimeters
An inch (in) is commonly used in the United States and in many product, engineering and everyday measurement contexts. A millimeter (mm) is a metric unit equal to one-thousandth of a meter and is widely used for small dimensions.
Because the two systems are different, converting inches to millimeters is useful when comparing imperial measurements with metric specifications.
For example, a product dimension listed as 10 inches corresponds to 254 millimeters.
Where Is Inches to MM Conversion Used?
An inch-to-mm conversion can be useful for:
- Engineering drawings
- Manufacturing measurements
- Hardware and fastener sizes
- Construction measurements
- Product dimensions
- Mechanical parts
- DIY projects
- CAD and technical drawings
- Screen and display measurements
- Comparing imperial and metric specifications
For technical work, keeping the full precision until the final step can help avoid unnecessary rounding.
Inches to MM vs MM to Inches
The two conversions use opposite operations.
Inches to MM
mm = inches × 25.4
MM to Inches
inches = mm ÷ 25.4
For example:
10 inches × 25.4 = 254 mm
And in reverse:
254 mm ÷ 25.4 = 10 inches
If you need the reverse conversion, use our MM to Inches Converter.
Quick Reference
Remember this simple conversion:
1 inch = 25.4 mm
So:
Inches × 25.4 = Millimeters
If you need to convert a measurement back from millimeters to inches:
Millimeters ÷ 25.4 = Inches
Frequently Asked Questions
How many millimeters are in 1 inch?
There are exactly 25.4 millimeters in 1 inch.
What is the formula for inches to mm?
The formula is:
mm = inches × 25.4
Multiply your inch measurement by 25.4 to get millimeters.
How many mm is 5 inches?
5 inches equals 127 mm.
Calculation:
5 × 25.4 = 127 mm
How many mm is 10 inches?
10 inches equals 254 mm.
Calculation:
10 × 25.4 = 254 mm
How many mm is 12 inches?
12 inches equals 304.8 mm.
How do I convert mm back to inches?
Divide the millimeter value by 25.4:
inches = mm ÷ 25.4
For example:
254 mm ÷ 25.4 = 10 inches
Is 1 inch exactly 25.4 mm?
Yes. The international definition establishes one inch as exactly 25.4 millimeters.
What does “in” mean in measurements?
In is the standard abbreviation for inch or inches.
What does “mm” mean?
mm is the abbreviation for millimeter, a metric unit of length equal to one-thousandth of a meter.