Inches to MM Converter
Convert inches to millimeters instantly — accurate, easy to use, free
The Answer
Quick Answer: Convert Inches to MM
1 inch equals exactly 25.4 millimeters. To convert inches to mm, simply multiply the inch value by 25.4. This is the international standard adopted in 1959, making the inches-to-millimeters conversion mathematically precise.
For example: 2 inches × 25.4 = 50.8 mm. 5 inches × 25.4 = 127 mm. 10 inches × 25.4 = 254 mm.
How Many MM in an Inch?
There are exactly 25.4 millimeters in 1 inch. This is not an approximation — it is the exact definition of an inch established by international agreement in 1959. Before this standardization, different countries had slightly different inch measurements, causing confusion in international trade and engineering.
The Exact Value
1 inch = 25.4 mm (exact)
1 inch = 2.54 cm
1 inch = 0.0254 meters
1 inch = 25,400 micrometers
How to Convert Inches to Millimeters
Converting inches to millimeters uses a simple multiplication:
Step-by-Step Guide
- Take your inch measurement
- Multiply it by 25.4
- The result is millimeters
Example Calculations
Convert 3 inches to mm:
Convert 5.5 inches to mm:
Convert 12 inches (1 foot) to mm:
Common Inches to MM Conversions
| Inches | Millimeters | Centimeters |
|---|---|---|
| 1/16″ | 1.5875 mm | 0.16 cm |
| 1/8″ | 3.175 mm | 0.32 cm |
| 1/4″ | 6.35 mm | 0.64 cm |
| 1/2″ | 12.7 mm | 1.27 cm |
| 3/4″ | 19.05 mm | 1.91 cm |
| 1″ | 25.4 mm | 2.54 cm |
| 2″ | 50.8 mm | 5.08 cm |
| 3″ | 76.2 mm | 7.62 cm |
| 4″ | 101.6 mm | 10.16 cm |
| 5″ | 127 mm | 12.7 cm |
| 6″ | 152.4 mm | 15.24 cm |
| 8″ | 203.2 mm | 20.32 cm |
| 10″ | 254 mm | 25.4 cm |
| 12″ (1 ft) | 304.8 mm | 30.48 cm |
| 18″ | 457.2 mm | 45.72 cm |
| 24″ (2 ft) | 609.6 mm | 60.96 cm |
| 36″ (3 ft/1 yd) | 914.4 mm | 91.44 cm |
Popular Inch Fractions to Millimeters
| Fraction | Decimal Inches | Millimeters |
|---|---|---|
| 1/64″ | 0.0156″ | 0.397 mm |
| 1/32″ | 0.0313″ | 0.794 mm |
| 1/16″ | 0.0625″ | 1.588 mm |
| 3/32″ | 0.0938″ | 2.381 mm |
| 1/8″ | 0.125″ | 3.175 mm |
| 5/32″ | 0.156″ | 3.969 mm |
| 3/16″ | 0.188″ | 4.763 mm |
| 1/4″ | 0.25″ | 6.35 mm |
| 5/16″ | 0.313″ | 7.938 mm |
| 3/8″ | 0.375″ | 9.525 mm |
| 7/16″ | 0.438″ | 11.113 mm |
| 1/2″ | 0.5″ | 12.7 mm |
| 5/8″ | 0.625″ | 15.875 mm |
| 3/4″ | 0.75″ | 19.05 mm |
| 7/8″ | 0.875″ | 22.225 mm |
Common Uses for Inches to MM Conversion
Woodworking and Carpentry
Converting inches to mm is essential when working with international woodworking plans, metric-spec tools, or European hardware. Many CNC and precision woodworking tools use millimeters.
Engineering and Manufacturing
The inches to millimeters conversion is critical in engineering, especially for parts sourced globally. Automotive, aerospace, and machinery specifications often need conversion between imperial and metric.
3D Printing
3D printer designs downloaded from US sources are often in inches, but most 3D printer slicers use millimeters. Converting inches to mm is a daily task for 3D printing hobbyists.
Automotive
Imported cars use metric specifications. Converting inch measurements to millimeters helps when working with foreign vehicles, imported parts, or aftermarket accessories.
Sewing and Tailoring
Pattern making, seam allowances, and fabric measurements often mix inches and millimeters. Precision sewing benefits from accurate conversion.
Construction
Modern architectural drawings increasingly use metric measurements. Converting traditional inch measurements to millimeters ensures accuracy in building.
Jewelry Making
Beads, wire gauges, chain lengths, and gemstone dimensions are often given in millimeters in international sources, while US suppliers may use inches.
Frequently Asked Questions: Inches to MM
How many mm in an inch?
There are exactly 25.4 millimeters in 1 inch. This is the international standard defined in 1959.
How do I convert inches to mm?
To convert inches to millimeters, multiply the inch value by 25.4. For example, 3 inches × 25.4 = 76.2 mm.
How many mm in a quarter inch?
1/4 inch equals 6.35 mm. Multiply 0.25 (decimal for 1/4) by 25.4 to get 6.35 mm.
How many mm in a half inch?
1/2 inch equals 12.7 mm. Half of 25.4 mm is 12.7 mm.
How many mm in a foot?
1 foot (12 inches) equals 304.8 mm. Multiply 12 × 25.4 = 304.8 mm.
Is 25 mm equal to 1 inch?
Not exactly. 25 mm is 0.9843 inches, while 1 inch is 25.4 mm. The difference is 0.4 mm (about 0.0157 inches). For most casual purposes they can be used interchangeably.
What is 6 inches in mm?
6 inches equals 152.4 mm. Calculation: 6 × 25.4 = 152.4 mm.
What is 10 inches in mm?
10 inches equals 254 mm. Calculation: 10 × 25.4 = 254 mm.
How accurate is the inches to mm conversion?
The conversion is mathematically exact because 1 inch = 25.4 mm by definition. Our converter provides results accurate to 4 decimal places.
Where did 25.4 come from?
The value 25.4 was chosen in the 1959 International Yard and Pound Agreement to standardize measurements between English-speaking countries. Before this, different countries had slightly different inch definitions.