Conversion Result
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Inches (in)
About This Converter
- What it does
- Converts millimeters to decimal inches with reverse conversion.
- Input
- Length in millimeters (mm)
- Output
- Decimal inches (in); reverse mm value
- Formula
- inches = mm ÷ 25.4 (since 1 in = 25.4 mm exactly)
- Last updated
About Millimeters to Inches Conversion
Millimeters are the go-to unit for small precision measurements in engineering, manufacturing, and scientific work globally. Inches remain standard in the United States and for many industries there. Converting millimeters to inches is essential when sourcing US parts from metric designs, working with imperial tools, or comparing specifications from different markets.
Conversion Formula
inches = mm ÷ 25.4
One inch equals exactly 25.4 mm, so divide millimeters by 25.4 to get inches. To convert inches to mm, multiply by 25.4.
Worked Example
Convert 50 mm to inches: 50 ÷ 25.4 = 1.9685 inches, approximately 2 inches. A 10 mm metric bolt ≈ 0.394 in (close to 3/8 in).
Common Use Cases
- Matching a metric screw (e.g. M10 = 10 mm) to the nearest imperial size for US hardware stores
- 3D printing: converting mm dimensions from a metric model to inches for an imperial design tool
- Printing: paper thickness in mm converted to inches for US printers
- Bicycle tire widths in mm (e.g. 25 mm road tire) converted to inches for US-labelled rims
- Optics and photography: sensor sizes in mm (e.g. 35 mm film) to inches for US accessories
Frequently Asked Questions
1 mm = 1 ÷ 25.4 = 0.039370 inches.
10 ÷ 25.4 = 0.3937 inches, close to 3/8 inch (0.375 in).
25 ÷ 25.4 = 0.9843 inches, approximately 1 inch.
50 ÷ 25.4 = 1.9685 inches, approximately 2 inches.
100 ÷ 25.4 = 3.937 inches, approximately 3 and 15/16 inches.
1 inch = 25.4 mm exactly.
6 ÷ 25.4 = 0.2362 inches, close to 15/64 inch.
12 ÷ 25.4 = 0.4724 inches, close to 15/32 inch.
Important Notes
- 1 mm = 0.039370 inches exactly (since 1 in = 25.4 mm).
- Common metric to inch approximations: 6 mm ≈ 15/64 in, 10 mm ≈ 3/8 in, 12 mm ≈ 15/32 in.
- Results are shown to 6 decimal places for precision engineering use.
- For cm to inches, use the cm to Inches converter — 1 cm = 10 mm.