MM to Inches Converter: Instant Results in Decimal and Fraction

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Looking for a quick way to mm to inch convert without memorizing formulas? This page explains how to convert millimeter and inches in seconds, with clear examples, a handy reference table, and FAQs. Use the mm inches conversion calculator above to get instant results and a fraction reading for practical work.

MM to Inch Converter

Convert millimeters ⟷ inches instantly — centered approx answers

Millimeters ⟷ Inches

Millimeters (mm)

Inches (in)

≈ – inches
≈ – fraction inches
≈ – feet & inches

Other Converted Values

Centimeters–
Meters–
Feet–
Yards–

How to convert mm to inch

  • Core formula: inches = millimeters ÷ 25.4
  • Why 25.4? By definition, 1 inch equals exactly 25.4 millimeters.

Examples:

  • 100 mm in inches = 100 ÷ 25.4 = 3.9370″
  • 150 mm to inch = 150 ÷ 25.4 = 5.9055″
  • 3 mm to inch = 3 ÷ 25.4 = 0.1181″

Tip: For woodworking or hardware, use the fraction output (nearest 1/64″) for tape-measure accuracy.

Quick mm to Inches reference table (common values)

Millimeters (mm)Inches (in)
10 mm0.3937″
25.4 mm1″
50 mm1.9685″
75 mm2.9528″
100 mm3.9370″
150 mm5.9055″
200 mm7.8740″
300 mm11.8110″
500 mm19.6850″
600 mm23.6220″
700 mm27.5591″
900 mm35.4331″

Use the calculator for any custom value—these are just starting points.

  • 200 mm in inch = 7.8740″
  • 500 mm in inch = 19.6850″
  • 600 mm in inch = 23.6220″
  • 700 mm in inch = 27.5591″
  • 900 mm in inch = 35.4331″
  • 100 mm to inch = 3.9370″
  • 10 mm in inch = 0.3937″

Reverse: convert inch to mm

Need inches to mm instead? Multiply by 25.4.

  • mm = inches × 25.4
  • mm in 12 inch = 12 × 25.4 = 304.8 mm
  • mm in 3 inch = 3 × 25.4 = 76.2 mm
  • mm in 4 inch = 4 × 25.4 = 101.6 mm
  • mm in 2 inch = 2 × 25.4 = 50.8 mm

Fraction vs decimal: when to use which

  • Decimal inches (e.g., 3.9370″) are perfect for CAD, CNC, and specifications.
  • Fraction inches (e.g., 3 15/16″) are better on the job site or when reading a tape.
    The calculator shows both to remove guesswork.

FAQ: millimeter and inches

How many mm in 1 inch?

1 inch = 25.4 mm (exact). This is the international standard definition.

How do I convert mm to inches quickly?

Use the formula: inches = millimeters ÷ 25.4. Example: 32 mm ÷ 25.4 = 1.2598″.

How do I convert inches to mm?

Multiply by 25.4. Example: 2″ × 25.4 = 50.8 mm.

How many mm are in 3 inch?

3 inches = 76.2 mm.

How many mm are in 4 inch?

4 inches = 101.6 mm.

How many mm are in 12 inch (1 foot)?

12 inches = 304.8 mm.

What is 3 mm to inch?

3 mm = 0.1181″.

Is 25.4 mm really exactly 1 inch?

Yes. Since 1959, 1 inch has been defined internationally as exactly 25.4 millimeters.

Should I use decimal inches or fractional inches?

Use decimal inches for CAD/CNC/engineering specs (e.g., 3.9370″). Use fractional inches for tape measures and on‑site work (e.g., ≈ 3 15/16″).

Why does the fraction sometimes look slightly different from the decimal?

The fraction is an approximation to the nearest 1/64″. It’s designed for practical measuring, so tiny differences from the exact decimal are normal and expected.

What’s the easiest way to avoid mistakes when converting?

Enter the value in the calculator, copy the decimal inch for specifications, and use the fraction line for physical measuring. This gives both precision and practicality.

            Why this converter?

            • Accurate mm in inches and inches to mm conversions
            • Fraction readout for real-world measuring
            • Clear layout for quick scanning and fewer mistakes

            Bookmark this page for the next time you need to convert mm to inch fast.