Inches to MM Converter
How to convert inches to mm
To convert inches to millimeters, multiply the inch value by 25.4 (mm = in × 25.4), because 1 inch is defined as exactly 25.4 millimeters.
Quick reference table
| Inch (in) | Millimeter (mm) |
|---|---|
| 1 | 25.4 |
| 5 | 127 |
| 10 | 254 |
| 25 | 635 |
| 50 | 1270 |
| 100 | 2540 |
Frequently Asked Questions
What are 1/4 inch and 3/8 inch in millimeters?
1/4 inch equals 6.35 mm and 3/8 inch equals 9.525 mm. That helps when a US screw, socket, or hex key size needs a metric substitute at a local hardware store.
Why convert a 5/16 drill bit or a 0.016 inch spec to mm?
A 5/16 inch drill bit is 7.9375 mm, and 0.016 inch is about 0.4064 mm. Those conversions are useful for imported part tolerances, CNC drawings, and 3D printing specs where your tools and stock are labeled in metric sizes.
More length conversions
The Ultimate Slack-Off Tool!
Stealth-watch videos & listen to novels
No card needed. Try it right now.
Love it? One coffee = lifetime access.
Windows 11 / 10 only
Why use a real-time, two-way length converter?
Metric units like centimeters, meters and kilometers still coexist worldwide with imperial units like inches, feet, yards and miles. Whether you're checking furniture dimensions from an overseas store, converting a suitcase's inch spec, or comparing a child's height to international charts, mentally converting cm to inches or meters to feet is error-prone. This tool lets you pick a unit and type a value on either side — the other side updates instantly, no "calculate" button required.
Whenever you change a unit, the tool automatically saves your last-used pair to the browser's localStorage, so the next visit starts right where you left off.
Common length conversion factors
- 1 centimeter (cm) = 10 millimeters (mm)
- 1 meter (m) = 100 centimeters (cm)
- 1 kilometer (km) = 1,000 meters (m)
- 1 inch (in) = 2.54 centimeters (cm)
- 1 foot (ft) = 12 inches (in) = 30.48 centimeters
- 1 yard (yd) = 3 feet (ft) = 0.9144 meters
- 1 mile = 1,760 yards (yd) = 1.609344 kilometers
Where metric and imperial units come from
The modern meter is defined by international agreement as part of the International System of Units (SI), while inches, feet, yards and miles belong to the imperial system, still widely used in the US and parts of the UK (home dimensions, height/weight, road distances). Knowing the exact ratios helps when shopping internationally, traveling abroad, or reading English technical specs.
Typical use cases
US-market monitors, furniture and clothing are often labeled in inches, while many other countries use centimeters and meters for room measurements and renovation planning; treadmill displays, maps and flight distances may mix miles and kilometers. Switch either side to any of the 8 supported units to cover everyday and professional conversion needs.
Inches to MM Converter
Use this direction when inch fractions appear on imported tools or parts, but the fasteners, cutters, drill bits, and shop inventory available to you are mostly metric.
The Ultimate Slack-Off Tool!
Stealth-watch videos & listen to novels
No card needed. Try it right now.
Love it? One coffee = lifetime access.
Windows 11 / 10 only