Inches to Millimeters Converter
Type a value in inches to get it in millimeters, and see the reverse conversion.
Your numbers
Your results
Converted value
Millimeters (mm)
—
1 in in mm
—
Your number read as mm, in in
—
Centimetres (cm)
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Inches to Millimeters Converter by TheCalcTools
How the Inches to Millimeters Converter works
Imperial fractions such as 1/8 or 3/8 inch are common for drill bits, sockets and plywood. Multiply by 25.4 to get exact millimetres.
To convert inches to millimeters, multiply by 25.4. The calculator shows the result to 6 significant figures; the conversion factor itself is exact by definition.
Quick estimate in your head: a quarter inch is about 6.35 mm.
The formula
mm = in × 25.4in = mm ÷ 25.4
Worked example
Using the default values shown in the calculator:
| Value in inches (in) | 0.25 |
|---|
- 0.25 in × 25.4 = 6.35 mm.
Result:
| Millimeters (mm) | 6.35 |
|---|---|
| 1 in in mm | 25.4 |
| Your number read as mm, in in | 0.00984252 |
| Centimetres (cm) | 0.635 |
Conversion table
| in | mm |
|---|---|
| 0.0625 in | 1.5875 mm |
| 0.125 in | 3.175 mm |
| 0.25 in | 6.35 mm |
| 0.375 in | 9.525 mm |
| 0.5 in | 12.7 mm |
| 0.625 in | 15.875 mm |
| 0.75 in | 19.05 mm |
| 1 in | 25.4 mm |
| 1.5 in | 38.1 mm |
| 2 in | 50.8 mm |
Frequently asked questions
What is 1 inch in millimeters?
1 inch (in) equals 25.4 mm.
Sources and further reading
- Wikipedia: Inch
- Wikipedia: Foot (unit)
- NIST: Guide for the Use of the International System of Units (SI)
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.