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High-Precision Conversion

Millimeters to Inches

A free mm to inches calculator with engineering-grade accuracy for manufacturing, architecture, and design. Instant results with zero margin for error.

mm
3.937008
in

≈ 3 15/16" (nearest 1/16)

1 in = 25.4 mm · tolerance ±0.0001

5 mm10 mm12 mm15 mm16 mm20 mm25 mm30 mm40 mm50 mm

01

Exact precision

Built on the international inch: 1 in = 25.4 mm. Accurate to 6 decimals.

02

Printable chart

A full mm-to-inches chart with decimal and 1/16″ fractions ready to print.

03

400+ preset pages

Dedicated, SEO-friendly page for every popular value from 0.1 mm to 4000 mm.

Popular values

Millimeters → Inches

Jump straight to the most-searched conversions.

5 mm= 0.1969″10 mm= 0.3937″12 mm= 0.4724″15 mm= 0.5906″16 mm= 0.6299″20 mm= 0.7874″25 mm= 0.9843″30 mm= 1.1811″40 mm= 1.5748″50 mm= 1.9685″60 mm= 2.3622″80 mm= 3.1496″100 mm= 3.937″150 mm= 5.9055″200 mm= 7.874″250 mm= 9.8425″300 mm= 11.811″500 mm= 19.685″1000 mm= 39.3701″

Reverse conversions

Inches → Millimeters

From common fractions to whole inches.

0.25″= 6.35 mm0.5″= 12.7 mm0.75″= 19.05 mm1″= 25.4 mm1.25″= 31.75 mm1.5″= 38.1 mm1.75″= 44.45 mm2″= 50.8 mm2.25″= 57.15 mm2.5″= 63.5 mm3″= 76.2 mm3.5″= 88.9 mm4″= 101.6 mm5″= 127 mm6″= 152.4 mm8″= 203.2 mm10″= 254 mm12″= 304.8 mm
See all inches → mm

FAQ

Common questions

How do I convert mm to inches?+

Divide the millimeter value by 25.4. For example, 100 mm ÷ 25.4 = 3.937 in. Our converter does this instantly and also shows the nearest fractional inch (1/16, 1/32, 1/64).

How do I convert inches to mm?+

Multiply inches by 25.4. Example: 2.5 in × 25.4 = 63.5 mm.

Is 1 inch exactly 25.4 mm?+

Yes. Since 1959 the international inch has been defined as exactly 25.4 millimeters, making every conversion between the two units deterministic.

What is 10 mm in inches?+

10 mm equals 0.3937 inches, or about 25/64″.

What is 2.5 inches in mm?+

2.5 inches equals exactly 63.5 mm.