Inches to millimeters converter

1 in = 25.4 mm (exact). To convert inches to millimeters, multiply by 25.4. Example: 10 in = 254 mm.

Result (mm)

mm = in × 25.4 · Swap: Millimeters to inches

Open the full tool: Unit converter →

Inches to millimeters chart

InchesMillimeters
0.125 in3.175 mm
0.25 in6.35 mm
0.375 in9.525 mm
0.5 in12.7 mm
0.625 in15.875 mm
0.75 in19.05 mm
1 in25.4 mm
1.25 in31.75 mm
1.5 in38.1 mm
2 in50.8 mm
2.5 in63.5 mm
3 in76.2 mm
4 in101.6 mm
5 in127 mm
6 in152.4 mm
8 in203.2 mm
10 in254 mm
12 in304.8 mm

How to convert inches to millimeters

Formula: mm = in × 25.4. Worked example: 10 in = 254 mm.

About these units

Millimeters are the natural unit for small inch sizes: drill bits, bolts, board thickness, plumbing (½″, ¾″). One inch is exactly 25.4 mm; fractional inches such as 1/8, 1/4 or 3/8 convert by multiplying the fraction by 25.4.

Category: length. Results on this page are calculated in your browser and rounded to 7 significant digits; the table above uses 6. For other units of length open the full unit converter, or use the reverse page — millimeters to inches.

FAQ

How many millimeters are in one in?

1 in = 25.4 mm exactly. Conversely, 1 mm = 0.03937008 in.

What is 100 in in millimeters?

100 in = 2540 mm.

Is this converter accurate?

Yes — it uses the official definitions (1 in = 0.0254 m, 1 mm = 0.001 m) and shows results rounded to 7 significant digits.

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