Millimeters to Inches Converter

Convert length between millimeters and inches, both directions on one page.

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Millimeters to Inches Converter

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To convert millimeters to inches, divide by 25.4; to convert inches to millimeters, multiply by 25.4. Like the cm-to-inch conversion, this is an exact figure, not a rounded one.

Millimeters are the go-to metric unit for anything needing real precision -- fastener sizes, pipe diameters, tolerances on manufactured parts, and imported hardware specs are commonly given in mm.

For larger measurements like room dimensions or lot sizes, the Centimeters to Inches or Feet to Meters converters are more practically sized units.

Where these numbers come from

Standard unit-conversion factors. Material weight figures (where used) are typical averages -- check your specific supplier for exact density.

Frequently asked questions

Why use millimeters instead of centimeters for precision work?

A millimeter is 10x smaller than a centimeter, giving finer resolution without needing decimals -- 'a 6mm gap' is cleaner to state and read than '0.6 cm'.

Are fastener sizes usually in mm?

Metric fasteners (common on imported hardware, appliances, and some specialty construction products) are sized in millimeters -- diameter and thread pitch both.

Is there a quick way to estimate mm to inches in my head?

Roughly, divide mm by 25 for a quick estimate (slightly overstates the true inch value, since 25.4 is the real number) -- fine for a rough check, not for a precise cut.

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Millimeters to Inches Converter