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Millimetres to Inches

1 millimetre = 0.03937 inches · 1 in = 25.4 mm

1 millimetre = 0.03937 inches

How it’s calculated

in = mm ÷ 25.4

  • Divide the value in millimetres by 25.4.
  • Equivalently, multiply by 0.03937007874.
  • 1 mm = 0.03937007874 in · 1 in = 25.4 mm
Show worked solutionFactor, unit cancellation and rounding, step by step

  1. Find the conversion factor

    By definition 1 mm = 0.001 m and 1 in = 0.0254 m, so 1 in = 25.4 mm. Source: BIPM SI Brochure (9th ed.); NIST SP 811 / Handbook 44.

  2. Multiply by the factor written as a fraction

    Put mm in the denominator so it cancels, leaving in.

  3. Calculate (unrounded)

  4. Round the answer

    Rounded to 5 significant figures.

Answer: 0.03937 in

1 mm in other units

Batch convert mm → in
Results
  1. 1 mm = 0.03937 in
  2. 5 mm = 0.19685 in
  3. 10 mm = 0.3937 in
  4. 25 mm = 0.98425 in

Permanent link to this conversion

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Quick examples

  • 1 millimetre = 0.03937 inches
  • 5 millimetres = 0.19685 inches
  • 10 millimetres = 0.3937 inches
  • 25 millimetres = 0.98425 inches
  • 100 millimetres = 3.937 inches

About these units

Millimetre (mm)

SI (metric)

Exactly 1/1 000 of a metre.

1 mm = 0.001 m

Source: BIPM SI Brochure (9th ed.)

Inch (in)

US & imperial (identical)

Exactly 2.54 cm (international inch, 1959).

1 in = 0.0254 m

Source: NIST SP 811 / Handbook 44

Millimetres to inches conversion table

millimetre (mm) to inch (in)
Millimetres (mm)Inches (in)
0.1 mm0.003937 in
0.5 mm0.019685 in
1 mm0.03937 in
2 mm0.07874 in
3 mm0.11811 in
4 mm0.15748 in
5 mm0.19685 in
6 mm0.23622 in
7 mm0.27559 in
8 mm0.31496 in
9 mm0.35433 in
10 mm0.3937 in
15 mm0.59055 in
20 mm0.7874 in
25 mm0.98425 in
30 mm1.1811 in
40 mm1.5748 in
50 mm1.9685 in
75 mm2.9528 in
100 mm3.937 in
250 mm9.8425 in
500 mm19.685 in
1,000 mm39.37 in

Related conversions

Frequently asked questions

How do I convert millimetres to inches?

Use in = mm ÷ 25.4. Divide the value in millimetres by 25.4.

How many inches are in 1 millimetre?

1 millimetre (mm) equals 0.03937 inches (in); more precisely 0.03937007874.

How many millimetres are in 1 inch?

1 inch (in) equals 25.4 millimetres (mm).

What is 10 mm in in?

10 millimetres = 0.3937 inches.

What is a millimetre?

Exactly 1/1 000 of a metre.

What is a inch?

Exactly 2.54 cm (international inch, 1959).

Formula: in = mm ÷ 25.4. Factors last reviewed 2026-10-27.