Inches-to-Millimeters Converter
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| Cale | Milimetry |
|---|---|
| 1 cala | 25,4 mm |
| 2 cala | 50,8 mm |
| 3 cala | 76,2 mm |
| 4 cala | 101,6 mm |
| 5 cala | 127 mm |
| 6 cala | 152,4 mm |
| 8 cala | 203,2 mm |
| 10 cala | 254 mm |
| 12 cala | 304,8 mm |
| 16 cala | 406,4 mm |
| 20 cala | 508 mm |
| A fraction of an inch | Milimetry |
|---|---|
| 1/16" | 1,5875 mm |
| 1/8" | 3,175 mm |
| 3/16" | 4,7625 mm |
| 1/4" | 6,35 mm |
| 5/16" | 7,9375 mm |
| 3/8" | 9,525 mm |
| 7/16" | 11,1125 mm |
| 1/2" | 12,7 mm |
| 9/16" | 14,2875 mm |
| 5/8" | 15,875 mm |
| 11/16" | 17,4625 mm |
| 3/4" | 19,05 mm |
| 13/16" | 20,6375 mm |
| 7/8" | 22,225 mm |
| 15/16" | 23,8125 mm |
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Other tools you may find usefulInch in engineering and technology – why do we convert it to millimeters?
An inch (in or ″) is an Anglo-Saxon unit of length, which in the international standard is exactly 25.4 millimeters. While centimeters are often used in consumer electronics (e.g. screen sizes), in technical sciences, mechanical engineering, hydraulics and pneumatics, the basic unit of measurement of the metric system is millimeter (mm). Precise conversion of inches to millimeters is crucial when fitting threads, selecting workshop wrenches, barrel calibers or pressure pipe diameters, where differences of the order of tenths of a millimeter determine the tightness and safety of the installation.
Our live inches to millimeters calculator allows you to convert units quickly and precisely. The tool supports whole values and fractions of inches (e.g. 1/2, 3/4), which makes the work of every mechanic, plumber or DIY enthusiast easier.
Inches (in) to millimeters (mm) conversion formula
The inches to millimeters converter is based on a fixed and unchanging definition:
1 inch = 25.4 mm
To convert inches (din) to millimeters (dmm), multiply the number of inches by 25.4:
dmm= din× 25.4
To convert to a fraction of an inch, first convert it to a decimal, then multiply by 25.4 (e.g. 3/8" = 0.375 × 25.4 = 9.525 mm).
The reverse operation - converting millimeters to inches - requires dividing the value in millimeters by 25.4:
din= dmm/ 25.4
Conversion table: fractions of inches to millimeters (mm)
In hydraulics and mechanics, fractional inches are most often used. The table below shows the exact conversion of these dimensions to millimeters:
| Dimension in inches (in) | Decimal inch | Dimension in millimeters (mm) | Practical use / Examples |
|---|---|---|---|
| 1/8" | 0.125" | 3.18 mm | Small precision screws, pressure gauge threads |
| 1/4" | 0.250" | 6.35 mm | Popular bit socket in screwdrivers or small socket wrenches. |
| 3/8" | 0.375" | 9.53 mm | Medium-sized socket wrenches, pneumatic installations. |
| 1/2" | 0.500" | 12.70 mm | Standard garden hoses, large socket wrenches, water pipes |
| 3/4" | 0.750" | 19.05 mm | Connection pipes in domestic water installations, thick hoses. |
| 1" | 1.000" | 25.40 mm | Diameter of pipes, firearm caliber. |
| 1 1/4" | 1.250" | 31.75 mm | Drain pipes for washbasins and bathroom traps. |
| 2" | 2.000" | 50.80 mm | Main pipes sewage, car exhaust diameters. |
Application of the inch to millimeter converter in plumbing and industry
Understanding the in to mm converter is necessary in several areas:
- Inch and metric threads:Tools and screws manufactured in the USA (UNC, UNF threads) have inch dimensions. Attempting to screw a metric screw into an inch socket destroys the thread.
- Domestic and industrial plumbing:Although pipes are specified in inches, the actual outside diameters of standardized steel pipes are given in millimeters (e.g. a 1" steel pipe has approximately 33.7 mm outside diameter).
- Photography and optics:Thread diameters of photographic filters and camera matrices (e.g. 1 inch, 1/1.7 inch) are given in inches, but filters are purchased custom-made in mm.
Frequently asked questions (FAQ)
How many millimeters is exactly one inch?
One international inch is exactly 25.4 millimeters.
How to write 1/2 inch in millimeters?
Mathematically, 1/2 inch is exactly 12.7 mm (0.5 × 25.4). However, in plumbing, 1/2" threaded steel pipe has an outer diameter of approximately 21 mm due to the specificity of pipe standards.
Why is a 1" inch pipe 33.7 mm and not 25.4 mm?
Historically, 1 inch was the diameter of the hole inside the pipe (pipe lumen), given the wall thickness of the time. As technology allowed for thinner walls over time while maintaining the same internal diameter, the external diameter remained the same (in this case 33.7 mm for a 1" steel pipe).
How to quickly convert inches to mm in memory?
The easiest way is to multiply the number of inches by 25. For example: 2 inches is 2 × 25 = 50 mm (the exact result is 50.8 mm), which is sufficient for most approximate applications.
What does the inch symbol mean and how to insert it?
An inch is marked with a double quotation mark symbol (e.g. 2") or the professional prime sign (″). The abbreviation in English is "in".