Inches to Millimeters
Convert inches to millimeters instantly — multiply the inches by 25.4. Type in either box to convert both ways. Common for tools, drill bits and DIY plans that list sizes in inches but need millimeters.
Inches to Millimeters conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 0.25 in | 6.35 mm |
| 0.5 in | 12.7 mm |
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 4 in | 101.6 mm |
| 6 in | 152.4 mm |
| 12 in | 304.8 mm |
| 24 in | 609.6 mm |
How to convert inches to millimeters
To convert inches to millimeters, multiply the inches by 25.4. For example, 1 in equals 25.4 mm. The calculator above runs the exact factor at full precision and updates as you type, and the swap button flips the direction so you can go from millimeters back to inches just as quickly.
Frequently asked questions
How do you convert inches to millimeters?
To convert inches to millimeters, multiply the inches by 25.4. For example, 1 in is 25.4 mm. The calculator above does this for you the moment you type — enter a value on the left and the millimeters result appears on the right, and you can type in either box to convert in the opposite direction. Every result uses the exact internationally defined factor, not a rounded shortcut, so the numbers are accurate enough for schoolwork, cooking, travel and engineering alike.
How many millimeters are in 1 in?
There are 25.4 mm in 1 in, and inches scale to millimeters in that same fixed ratio at any size. The conversion table on this page lists the most common values — 0.25 in is 6.35 mm, and the table continues up to 24 in = 609.6 mm — so you can read off everyday amounts at a glance without typing anything. Values that fall between those rows convert just as exactly, because the calculator carries the full factor rather than the rounded figures printed here.
Is this in to mm converter accurate?
Yes — this in to mm converter is accurate. It uses the precise, internationally agreed conversion factor rather than a rounded approximation, and the math runs at full double precision in your browser, with results shown to six significant figures. Common for tools, drill bits and DIY plans that list sizes in inches but need millimeters.
Is the inches to millimeters converter free?
Yes — the inches to millimeters converter is completely free, with no sign-up and no limit on how many conversions you run. Every calculation happens locally in your browser, so nothing you type is uploaded or stored. For other units, the full LK Forge unit converter covers length, weight, temperature, volume and speed in one place.
More conversions
Millimeters → InchesFeet → MetersGrams → OuncesOunces → GramsMilliliters → Fluid OuncesFluid Ounces → Milliliters All units →
Reference: full unit conversion chart · metric vs imperial, explained