Inches to Millimeters Conversion Table — Fractional & Decimal (1/64" to 50")
Complete reference: 64 fractional sizes + whole inches 1-50
Any length-distance value in in can be converted to mm using the conversion factor:
- 1 inch = 25.4 millimeter
- mm = in x 25.4
in → mm Quick Converter
Need more features? Try our complete inch to millimeter converter.
Conversion Chart Image
Download Options
What is Inch (in)?
Imperial/US customary unit standardized as exactly 25.4 millimeters since 1959.
What is Millimeter (mm)?
Metric unit equal to one thousandth (1/1000) of a meter.
How to Convert Inch to Millimeter
Example
Convert 6 in to mm:
6 × 25.4 = 152.4 mm
Inches to Millimeters Conversion Table — Fractional & Decimal (1/64" to 50")
Values from 1 to 50 in.
Fractional Inches to Millimeters
Standard fractional inch values used in hardware, drill bits, machining, and engineering — with decimal inch and millimeter equivalents. All values exact (1 in = 25.4 mm).
| Fraction | Decimal (in) | mm |
|---|---|---|
| 1/64" | 0.0156 | 0.397 |
| 1/32" | 0.0313 | 0.794 |
| 3/64" | 0.0469 | 1.191 |
| 1/16" | 0.0625 | 1.588 |
| 5/64" | 0.0781 | 1.984 |
| 3/32" | 0.0938 | 2.381 |
| 7/64" | 0.1094 | 2.778 |
| 1/8" | 0.1250 | 3.175 |
| 9/64" | 0.1406 | 3.572 |
| 5/32" | 0.1563 | 3.969 |
| 11/64" | 0.1719 | 4.366 |
| 3/16" | 0.1875 | 4.763 |
| 13/64" | 0.2031 | 5.159 |
| 7/32" | 0.2188 | 5.556 |
| 15/64" | 0.2344 | 5.953 |
| 1/4" | 0.2500 | 6.350 |
| 17/64" | 0.2656 | 6.747 |
| 9/32" | 0.2813 | 7.144 |
| 19/64" | 0.2969 | 7.541 |
| 5/16" | 0.3125 | 7.938 |
| 21/64" | 0.3281 | 8.334 |
| 11/32" | 0.3438 | 8.731 |
| 23/64" | 0.3594 | 9.128 |
| 3/8" | 0.3750 | 9.525 |
| 25/64" | 0.3906 | 9.922 |
| 13/32" | 0.4063 | 10.319 |
| 27/64" | 0.4219 | 10.716 |
| 7/16" | 0.4375 | 11.113 |
| 29/64" | 0.4531 | 11.509 |
| 15/32" | 0.4688 | 11.906 |
| 31/64" | 0.4844 | 12.303 |
| 1/2" | 0.5000 | 12.700 |
| Fraction | Decimal (in) | mm |
|---|---|---|
| 33/64" | 0.5156 | 13.097 |
| 17/32" | 0.5313 | 13.494 |
| 35/64" | 0.5469 | 13.891 |
| 9/16" | 0.5625 | 14.288 |
| 37/64" | 0.5781 | 14.684 |
| 19/32" | 0.5938 | 15.081 |
| 39/64" | 0.6094 | 15.478 |
| 5/8" | 0.6250 | 15.875 |
| 41/64" | 0.6406 | 16.272 |
| 21/32" | 0.6563 | 16.669 |
| 43/64" | 0.6719 | 17.066 |
| 11/16" | 0.6875 | 17.463 |
| 45/64" | 0.7031 | 17.859 |
| 23/32" | 0.7188 | 18.256 |
| 47/64" | 0.7344 | 18.653 |
| 3/4" | 0.7500 | 19.050 |
| 49/64" | 0.7656 | 19.447 |
| 25/32" | 0.7813 | 19.844 |
| 51/64" | 0.7969 | 20.241 |
| 13/16" | 0.8125 | 20.638 |
| 53/64" | 0.8281 | 21.034 |
| 27/32" | 0.8438 | 21.431 |
| 55/64" | 0.8594 | 21.828 |
| 7/8" | 0.8750 | 22.225 |
| 57/64" | 0.8906 | 22.622 |
| 29/32" | 0.9063 | 23.019 |
| 59/64" | 0.9219 | 23.416 |
| 15/16" | 0.9375 | 23.813 |
| 61/64" | 0.9531 | 24.209 |
| 31/32" | 0.9688 | 24.606 |
| 63/64" | 0.9844 | 25.003 |
| 1" | 1.0000 | 25.400 |
All values derived from the exact definition: 1 inch = 25.4 mm (International Yard and Pound Agreement, 1959).
Frequently Asked Questions
How do I convert inches to millimeters?
To convert inches to millimeters, multiply the inch value by 25.4. For example, 3 inches x 25.4 = 76.2 millimeters.
Why is 25.4 the exact conversion factor?
The international inch is defined as exactly 25.4 millimeters since 1959. This is an exact definition, so conversions between inches and millimeters are always precise.
When is this conversion most useful?
Inches to millimeters conversion is essential for hardware and fastener sizes, drill bit specifications, PCB and electronics design, machining tolerances, and 3D printing where metric dimensions are needed from imperial specs.
What common drill bit sizes in inches equal in millimeters?
Common conversions include: 1/8 in = 3.175 mm, 1/4 in = 6.35 mm, 3/8 in = 9.525 mm, 1/2 in = 12.7 mm, and 1 in = 25.4 mm.
How accurate is this inches to millimeters conversion table?
This table is perfectly accurate as the conversion is based on the exact definition of 1 inch = 25.4 mm. No rounding or approximation is involved in this conversion.
