Millimeters to Inches Converter
There are 0.0393701 inches in one millimeter. To convert millimeters to inches, multiply by 0.0393701.
How to Convert Millimeters to Inches
To convert millimeters to inches, multiply by 0.0393701. For an exact result, divide by 25.4 instead.
For example: 5 millimeters × 0.0393701 = 0.19685 inches.
Where This Comes Up
Imported parts, camera filter threads, watch bands and metric fasteners are all labeled in millimeters. Converting to inches is what tells you whether the tools and stock in an American workshop will fit them.
A 20-millimeter watch lug is 0.787402 inches, which is just over 3/4 inch — the reason 3/4-inch straps are slightly loose in a 20 mm lug.
What People Get Wrong
Inch rulers are divided into sixteenths, not decimals, so a 0.63-inch answer is more usefully read as a shade over 5/8 inch. Multiply the decimal by 16 to get the nearest marking.
Millimeters to Inches Conversion Table
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 | 0.0393701 |
| 2 | 0.0787402 |
| 3 | 0.11811 |
| 4 | 0.15748 |
| 5 | 0.19685 |
| 6 | 0.23622 |
| 7 | 0.275591 |
| 8 | 0.314961 |
| 9 | 0.354331 |
| 10 | 0.393701 |
| 11 | 0.433071 |
| 12 | 0.472441 |
| 13 | 0.511811 |
| 14 | 0.551181 |
| 15 | 0.590551 |
| 16 | 0.629921 |
| 17 | 0.669291 |
| 18 | 0.708661 |
| 19 | 0.748031 |
| 20 | 0.787402 |
| 25 | 0.984252 |
| 30 | 1.1811 |
| 40 | 1.5748 |
| 50 | 1.9685 |
| 75 | 2.95276 |
| 100 | 3.93701 |
| 250 | 9.84252 |
| 500 | 19.685 |
| 1,000 | 39.3701 |
About These Units
The millimeter
A millimeter is one thousandth of a meter. It is the unit of choice for engineering drawings, rainfall and anything small enough that centimeters would need decimals.
The inch
The inch is exactly 2.54 centimeters by international agreement. Americans use it for screen sizes, lumber, rainfall, tire rims and body height together with feet.
Definitions follow NIST Special Publication 811, Appendix B. See how we calculate for the exact values and rounding rules.
Frequently Asked Questions
How many inches is 10 mm?
10 millimeters is 0.393701 inches, a little under 2/5 of an inch.
What is 25 mm in inches?
25 millimeters is 0.984252 inches, just under a full inch.
How do I read a millimeter answer on an inch ruler?
Multiply the decimal inches by 16 and round. 0.787 inches times 16 is 12.6, so it is between 12/16 and 13/16 of an inch.
How many millimeters are in a 16th of an inch?
One sixteenth of an inch is 1.5875 millimeters, so a millimeter is roughly two thirds of a 16th.