Millimetres to inches
Multiply millimetres by 0.0393701 to get inches.
10 mm = 0.393701 in
How to convert millimetres to inches
The inch is exactly 2.54 centimetres (0.0254 m), by the 1959 international agreement. The millimetre is one thousandth of a metre (10⁻³ m).
Worked example — 10 mm: 10 × 0.0393701 = 0.393701 in.
Millimetres to inches table
| Millimetres | Inches |
|---|---|
| 1 mm | 0.0393701 in |
| 2 mm | 0.0787402 in |
| 3 mm | 0.11811 in |
| 5 mm | 0.19685 in |
| 10 mm | 0.393701 in |
| 20 mm | 0.787402 in |
| 25 mm | 0.984252 in |
| 50 mm | 1.9685 in |
| 100 mm | 3.937 in |
Reverse and related
About millimetres and inches
Millimetre (mm)
1 mm = 0.0393701 inDefinition. One thousandth of a metre (10⁻³ m)
History and origin
The millimetre is one thousandth of a metre, defined with the rest of the decimal metric system in the 1790s. Its small size suits precise work.
Current use
Millimetres are used for rainfall, engineering tolerances, and the sizes of screws, hardware and printed parts.
Source: BIPM, The International System of Units (SI), 9th ed. (2019)
Inch (in)
1 in = 25.4 mmDefinition. Exactly 2.54 centimetres (0.0254 m), by the 1959 international agreement
History and origin
The inch takes its name from the Latin uncia, a twelfth part, and has always been one twelfth of a foot. The 1959 agreement fixed it at exactly 2.54 centimetres.
Current use
Inches are used for screen and TV sizes worldwide, and in the United States for height, lumber and hardware.
Source: International Yard and Pound Agreement (1959); NIST Handbook 44, App. C
Where people use this
Millimetres: rainfall, engineering tolerances, screws and hardware. Inches: screen sizes, height, lumber and hardware. 25.4 mm is exactly 1 inch.
Every value is carried to full double precision; the display is rounded.
Sources: International Yard and Pound Agreement (1959); NIST Handbook 44, App. C; BIPM, The International System of Units (SI), 9th ed. (2019).
Questions people ask
How many inches is 1 mm?
One millimetre is about 0.0394 inches. To convert mm to inches, divide by 25.4.
How many inches is 10 mm?
10 mm, which is one centimetre, is about 0.394 inches, just under half an inch.
What is 5 mm in inches?
5 mm is about 0.197 inches, just under a quarter inch.