Millimeters to Inches Converter

Use this converter to easily convert between Millimeters and Inches (mm to in).

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    Quick navigation:
  1. How many Millimeters equal one Inch?
  2. Difference between Millimeters and Inches
  3. How to convert Millimeters to Inches
  4. mm to in conversion table

    How many Millimeters equal one Inch?

Inches and millimeters both are units that measure length. The symbols used for them are respectively in (or ), and mm. The International System of Units (SI) has established with a treaty in 1959 that 1” is equal to 25.4 mm, or conversely – 1 mm is equal to approximately 0.03937 in.

    Difference between Millimeters and Inches

Millimeters and inches are length measurement units that have been adopted by different systems. The mm is a metric unit, while the inch is an imperial unit. Their application also differs according to the situation and the accuracy it demands. However, both of them are usually featured on a standard ruler.

Undoubtedly, the millimeter is the more precise unit as it is significantly smaller. It is 5/127 of an inch, and is used in tasks that call for greater attention to detail such as scientific research and calculations, in electronics, or in mechanics.

A millimeter can be defined as being the distance light travels in 1/299,792,458,000 seconds in vacuum. This is derived from the fact that a mm is 0.001 of a meter – the fundamental measurement unit according to the SI.

On the other hand, the inch is used throughout the world as a standardized unit of sizing display screens. Aside from that, it is a common measurement unit in the United States and Canada. In the UK, the inch (along with the foot) is the primary means of indicating distance, for example in road maps and signs.

In the past, a popular definition of the inch would be it being equal to the width of a man’s thumb. The inch we know today was adopted as a unit in 1930 by the British Standards Institution. Later on it was adopted by 17 other countries, among which the United States.

    How to convert Millimeters to Inches

Converting millimeters to inches is based on knowing the relationship between the two units.

One way to do that is by the formula:

mm x 0.0393700787 = in.

However, the easier equation to calculate is the following:

mm / 25.4 = in.

Mm to in conversion example

Sample task: convert 150 millimeters to inches. Solution:

mm / 25.4 = in
150 mm / 25.40 = 5.905512 in
End result:
150 mm is equal to 5.905512 in

    mm to in conversion table

mm to in conversion table
mm in
1 mm 0.039370 in
2 mm 0.078740 in
3 mm 0.118110 in
4 mm 0.157480 in
5 mm 0.196850 in
6 mm 0.236220 in
7 mm 0.275591 in
8 mm 0.314961 in
9 mm 0.354331 in
10 mm 0.393701 in
20 mm 0.787402 in
30 mm 1.181102 in
40 mm 1.574803 in
50 mm 1.968504 in
60 mm 2.362205 in
70 mm 2.755906 in
80 mm 3.149606 in
90 mm 3.543307 in
100 mm 3.937008 in
200 mm 7.874016 in
300 mm 11.811024 in
400 mm 15.748031 in
500 mm 19.685039 in
600 mm 23.622047 in
700 mm 27.559055 in
800 mm 31.496063 in
900 mm 35.433071 in
1,000 mm 39.370079 in


[1] NIST Special Publication 330 (2008) - "The International System of Units (SI)", edited by Barry N.Taylor and Ambler Thompson

[2] International Organization for Standardization (1993). ISO Standards Handbook: Quantities and units (3rd edition). Geneva: ISO. ISBN 92-67-10185-4.

Cite this converter & page

If you'd like to cite this online converter resource and information as provided on the page, you can use the following citation:
Georgiev G.Z., "mm to inch Converter", [online] Available at: URL [Accessed Date: 06 Jul, 2022].