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Millimeters (mm) to Inches (in) Conversion Calculator and Table

Millimeters (mm) and inches (in) are both units of length, making their conversions simple and straightforward; one just has to remember the actual relation of these units.

Over time, the length of an inch varied, but today, it is standardized in relation to meters and millimeters.

Published: February 2, 2024.

To convert millimeters (mm) to inches (in or "), write the value in millimeters and click 'Calculate':

Millimeters (mm) to Inches (in)

Millimeters (mm):

Inches (in):

To convert inches to millimeters, feel free to use our Inches (in) to Millimeters (mm) Conversion Calculator and Table article.

How To Convert Millimeters (mm) to Inches (in)

Over time, the exact length of the inch varied, but today, it is standardized and is defined as exactly:

1 inch (in) = 25.4 mm → 1 mm = 1/25.4 inch = 0.0393700787 inches = ~0.03937 inches

Thus, if You want to convert 15.34 mm to inches, You can write:

L(mm) = 15.34 mm = 15.34 / 2.54 in = 0.603937 inches

Similarly, we can calculate:

10 mm to inches:

10 mm = 10 / 25.4 in = 0.3937 inches

15 mm to inches:

15 mm = 15 / 25.4 in = 0.59055 inches

18 mm to inches:

18 mm = 18 / 25.4 in = 0.70866 inches

20 mm to inches:

20 mm = 20 / 25.4 in = 0.78740 inches

25 mm to inches:

25 mm = 25 / 25.4 in = 0.9842 inches

30 mm to inches:

30 mm = 30 / 25.4 in = 1.18110 inches

40 mm to inches:

40 mm = 40 / 25.4 in = 1.57480 inches

50 mm to inches:

50 mm = 50 / 25.4 in = 1.96850 inches

60 mm to inches:

60 mm = 60 / 25.4 in = 2.36220 inches

80 mm to inches:

80 mm = 80 / 25.4 in = 3.14960 inches

100 mm to inches:

100 mm = 100 / 25.4 in = 3.9370 inches

Millimeters (mm) to Inches (in) Conversion Table

The following chart contains the most common millimeter values converted to inches (in):

Millimeters (cm) Inches (in)
1 0.03937
5  0.19685
10  0.39370
20  0.78740
30  1.18110
50  1.96850
100  3.93700
200  7.87401
500  19.6850
1000  39.3700
10000  393.700


If You wish to convert values that are not in the table, please use the millimeters-to-inches conversion calculator.

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A Brief Intro to Millimeters and Inches

The units of measurement, millimeters and inches, are fundamental to countless fields, from construction and engineering to everyday life.

Each has a rich history, evolving from different systems of measurement and reflecting the cultural and scientific advancements of their origins.

History of Meters and Millimeters

The metric system, which includes the meter as its base unit of length, was developed during the French Revolution as part of a broader effort to standardize measurements in France and, eventually, worldwide.

The meter was initially defined in 1791 by the French Academy of Sciences as one ten-millionth of the distance from the North Pole to the Equator along the meridian through Paris. This definition aimed at universality and was based on the world itself.

In 1799, the first physical prototype of the meter, a platinum bar, was created. This standardization was a significant step away from the varied and inconsistent local measures previously used.

The introduction of the millimeter, as a subdivision of the meter, followed naturally. A millimeter is defined as one-thousandth of a meter, fitting neatly into the decimal and base-10 structure of the metric system.

The metric system's adoption was gradual, spreading from France to other countries over the 19th and 20th centuries, significantly aided by international agreements like the Metre Convention of 1875.

History of Inches and Its Standardization

The inch has a more diverse and complex history, rooted in the ancient systems of measurement used by the Anglo-Saxons, Romans, and other civilizations. The word "inch" itself comes from the Latin "uncia," meaning "one-twelfth part," reflecting its original conception as one-twelfth of a foot.

This division is thought to have its origins in the Roman measurement system, where an inch was defined as the width of a thumb.

Over centuries, the inch was used in England and other parts of the British Empire with slight variations in its exact length. The diversity in the size of inches used in different regions and for different purposes highlighted the need for standardization.

This need became especially pressing during the industrial revolution when precise and uniform measurements became crucial for manufacturing and engineering.

The modern definition of the inch was established in 1959 when the United States and countries of the Commonwealth of Nations agreed upon an international yard and pound agreement.

According to this agreement, the inch was defined as exactly 25.4 millimeters, effectively tying it to the metric system and ensuring consistency in measurements across the countries that adopted this standard.