Convert Millimeters to Inches
1 millimeter (mm) equals 0.03937007874 inches (in).
1 mm = 0.03937007874 in
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk millimeter to inch converter to paste a column from Excel.
How to Convert Millimeter to Inch
- 1 mm = 0.03937007874 in
- 1 in = 25.4 mm
- Example: convert 15 mm to in: 15 mm = 15 × 0.03937007874 in = 0.5905511811 in
Reference conditions. in: The international yard and pound agreement (1959) fixed 1 yard = 0.9144 m exactly, so the inch, foot and mile are exact.
Formula
in = mm × 0.03937007874016
or in = mm ÷ 25.4
Derivation from SI units:
- 1 mm = 10⁻³ m
- 1 in = 2.54 cm = 0.0254 m (exact)
- 1 mm = 0.001 m ÷ 0.0254 m per in = 0.03937007874016 in
Both units are defined exactly, so the factor is exact. Millimeter definition: millimeter; Inch definition: inch.
Worked examples
- 25.4 mm is exactly 1 in.
25.4 mm × 0.03937007874 = 1 in - A 6 mm drill bit is 0.2362204724 in, close to 15/64 in.
6 mm × 0.03937007874 = 0.2362204724 in
Millimeter to Inch conversion table
| Millimeters (mm) | Inches (in) |
|---|---|
| 0.1 mm | 0.003937007874 in |
| 0.5 mm | 0.01968503937 in |
| 1 mm | 0.03937007874 in |
| 2 mm | 0.07874015748 in |
| 3 mm | 0.1181102362 in |
| 5 mm | 0.1968503937 in |
| 6 mm | 0.2362204724 in |
| 8 mm | 0.3149606299 in |
| 10 mm | 0.3937007874 in |
| 12 mm | 0.4724409449 in |
| 15 mm | 0.5905511811 in |
| 16 mm | 0.6299212598 in |
| 20 mm | 0.7874015748 in |
| 25 mm | 0.9842519685 in |
| 25.4 mm | 1 in |
| 30 mm | 1.181102362 in |
| 50 mm | 1.968503937 in |
| 75 mm | 2.952755906 in |
| 100 mm | 3.937007874 in |
| 150 mm | 5.905511811 in |
| 300 mm | 11.81102362 in |
| 500 mm | 19.68503937 in |
| 1000 mm | 39.37007874 in |
Where it's used
Machinists and makers switch between metric drawings and inch tooling. Dividing millimetres by 25.4 gives inches; fractional inch sizes are then rounded to the nearest 1/64 or 1/32.
Millimeter to other length units
| Conversion | 1 mm equals |
|---|---|
| millimeter to meter | 0.001 m |
| millimeter to kilometer | 0.000001 km |
| millimeter to centimeter | 0.1 cm |
| millimeter to micrometer | 1000 µm |
| millimeter to nanometer | 1000000 nm |
| millimeter to angstrom | 10000000 Å |
| millimeter to mile | 6.213711922 × 10⁻⁷ mi |
| millimeter to yard | 0.001093613298 yd |
| millimeter to foot | 0.003280839895 ft |
| millimeter to inch | 0.03937007874 in |
| millimeter to mil | 39.37007874 mil |
| millimeter to nautical mile | 5.399568035 × 10⁻⁷ nmi |
Frequently asked questions
How do I convert mm to inches?
Divide by 25.4: 10 mm = 0.3937 in.
How many inches are in 1 millimeter?
1 mm = 0.03937007874 in.
How do I convert millimeters to inches?
Multiply the value in mm by 0.03937007874, or divide it by 25.4. For example, 15 mm × 0.03937007874 = 0.5905511811 in.
Is the mm to in conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 7, SI prefixes.
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "inch (in)".
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Millimeters to Inches. Retrieved October 17, 2026, from https://scientificconverters.com/length/millimeters-to-inches/
IEEE
Scientific Converters, "Convert Millimeters to Inches," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/length/millimeters-to-inches/