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Millimeters to Inches Converter

Convert millimeters to inches and inches to millimeters instantly. Precision converter for engineering and manufacturing.

mm

Inches

1

in

25.4 mm = 1 in

in = mm × 0.0393701

Millimeters to Inches: 1 mm equals 0.03937 in. To convert millimeters to inches, multiply by 0.03937 (in = mm × 0.0393701). For example, 10 mm = 0.393701 in.

How to Convert Millimeters to Inches

To convert from millimeters to inches, multiply the value by 0.03937. The conversion is linear, meaning doubling the input doubles the output.

Conversion Formula

  • Millimeters to Inches: in = mm × 0.0393701
  • Inches to Millimeters: mm = in ÷ 0.0393701

Millimeters to Inches Conversion Chart

Millimeters (mm)Inches (in)
0.10.003937
0.250.009843
0.50.019685
10.03937
20.07874
30.11811
50.19685
100.393701
200.787402
250.984252
501.968505
1003.93701
2509.842525
100039.3701

Understanding the Units

What is a Millimeter?

A millimeter is one thousandth of a meter (1 mm = 0.001 m).

Common contexts: engineering, manufacturing, medicine.

What is an Inche?

The inch is a US customary and imperial unit equal to exactly 25.4 millimeters by the 1959 international yard and pound agreement.

From Old English ynce, derived from Latin uncia ("twelfth"), originally a twelfth of a Roman foot.

Common contexts: construction, screen sizes, apparel.

Real-World Reference Points

Item Millimeters (mm) Inches (in)
Credit card thickness0.760.0299
Sharpened pencil tip10.0394
Grain of rice50.1969

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FAQ

How many inches are in a millimeter?

One millimeter equals approximately 0.0393701 inches.

How do I convert mm to inches for 3D printing tolerances?

Multiply the millimeter value by 0.0393701. For precision work, 0.1 mm equals about 0.00394 inches (roughly 4 thousandths of an inch).

What is 25.4 mm in inches?

Exactly 1 inch. The inch is defined as precisely 25.4 millimeters, so dividing any mm value by 25.4 gives the exact inch equivalent.

When should I use millimeters vs inches?

Millimeters are standard in engineering, medicine, and science worldwide. Inches are common in US construction, manufacturing, and hardware sizing.

How many inches are in 1 millimeter?

1 mm equals 0.03937 in.

How do you convert millimeters to inches?

Multiply the millimeter value by 0.03937. Formula: in = mm × 0.0393701.

How many inches are in 5 millimeters?

5 mm = 0.19685 in.

How do you convert inches back to millimeters?

Use the inverse formula: mm = in ÷ 0.0393701. For example, 1 in = 25.399986 mm.

What is the difference between Millimeter and Inch?

A millimeter is one thousandth of a meter (1 mm = 0.001 m). The inch is a US customary and imperial unit equal to exactly 25.4 millimeters by the 1959 international yard and pound agreement.