Mm to inches converter
Convert millimeters to inches instantly. 1 inch equals exactly 25.4 mm.
Converting mm to inches
Millimeters and inches overlap most in hardware, manufacturing, and photography. Outside the US, screws, drill bits, and lens filters are specified in mm. US tool catalogs use fractional inches. If you're matching a metric bolt to an imperial wrench or buying a lens filter, this is the conversion you need.
The exact ratio: 1 inch = 25.4 millimeters, defined by the 1959 international yard and pound agreement. To convert mm to inches, divide by 25.4. The ratio is exact — not rounded.
Hardware sizes
Common metric hardware sizes and their closest fractional inch equivalents:
| mm | Inches | Nearest fraction |
|---|---|---|
| 3 mm | 0.11811 in | ≈ 1/8" |
| 5 mm | 0.19685 in | ≈ 3/16" |
| 6 mm | 0.23622 in | ≈ 1/4" |
| 8 mm | 0.314961 in | ≈ 5/16" |
| 10 mm | 0.393701 in | ≈ 3/8" |
| 15 mm | 0.590551 in | ≈ 19/32" |
| 20 mm | 0.787402 in | ≈ 25/32" |
| 25 mm | 0.984252 in | ≈ 1" |
Camera lens filter sizes
Lens filters are sized in mm. Here's the inch equivalent and common camera type:
| mm | Inches | Camera type |
|---|---|---|
| 37 mm | 1.4567 in | Compact / action cam |
| 49 mm | 1.9291 in | Mirrorless (kit lens) |
| 58 mm | 2.2835 in | Mid-range mirrorless |
| 67 mm | 2.6378 in | Standard zoom |
| 72 mm | 2.8346 in | Pro zoom |
| 77 mm | 3.0315 in | Pro prime / zoom |
| 82 mm | 3.2283 in | Large aperture prime |
Frequently asked
Use the full length converter to convert between cm, meters, feet, inches, yards, miles, and more — all 14 units in one place.