Millimeters to Inches
Convert millimeters to inches instantly, or swap to convert inches to millimeters.
Results are provided as is, for general information. Check anything important before relying on it. See the Terms of Use.
About this tool
Convert millimeters (mm) to inches (in), or inches to millimeters, for screws and fasteners, drill bits, lens and filter sizes, sheet thickness or product dimensions. One inch is exactly 25.4 millimeters. Divide millimeters by 25.4 to get inches, or swap direction to multiply inches by 25.4. Choose automatic precision or 0, 2, 4 or 6 decimal places for the decimal result. When converting millimeters to inches, a rounded ruler fraction is also shown, and a chart below lists common fractions of an inch in millimeters.
How it works
inches = millimeters ÷ 25.4 millimeters = inches × 25.4
The international inch is exactly 25.4 millimeters. Keep that exact factor in the calculation and round only the displayed answer.
| Question | Working | Answer |
|---|---|---|
| 10 mm in inches | 10 ÷ 25.4 | 0.393701 in |
| 25 mm in inches | 25 ÷ 25.4 | 0.984252 in |
| 100 mm in inches | 100 ÷ 25.4 | 3.93701 in |
| 3/4 in in mm | 0.75 × 25.4 | 19.05 mm |
When to use it
Questions
How do I convert mm to inches?
Divide millimeters by 25.4. For example, 10 mm is approximately 0.393701 inches and 100 mm is approximately 3.93701 inches.
How many mm are in an inch?
Exactly 25.4 mm. The international inch is defined as 25.4 millimeters, so this is not a rounded factor.
How do I convert inches to mm?
Multiply inches by 25.4. For example, 3/4 inch is 0.75 × 25.4 = 19.05 mm, and 2 inches is 50.8 mm. Use Swap, then enter inches to convert in this direction.
What is 10 mm in fractions of an inch?
10 mm is approximately 0.393701 inches. At the default 1/16 inch step this rounds to 3/8 inch; at a 1/64 inch step it is 25/64 inch. A fraction is a rounded approximation and does not change the conversion factor.
Is 25 mm the same as 1 inch?
Almost. 25 mm is about 0.984252 inches, slightly less than 1 inch. Exactly 1 inch is 25.4 mm.