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

Inches (in) and millimeters (mm) 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 inches (in) to millimeters (mm), write the value in inches and click 'Calculate':

Inches (in) to Millimeters (mm)

Inches (in):

Millimeters (mm):

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

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

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 inches to millimeters, You can write:

L(in) = 15.34 in = 15.34 * 25.4 mm = 389.636 mm

Similarly, we can calculate:

2 inches to mm:

2 inches = 2 * 25.4 mm = 50.8 mm

3 inches to mm:

3 inches = 3 * 25.4 mm = 76.2 mm

5 inches to mm:

5 inches = 5 * 25.4 mm = 127 mm

6 inches to mm:

6 inches = 6 * 25.4 mm = 152.4 mm

10 inches to mm:

10 inches = 10 * 25.4 mm = 254 mm

12 inches to mm:

12 inches = 1 foot = 12 * 25.4 mm = 304.8 mm

21 inches to mm:

21 inches = 21 * 25.4 mm = 533.4 mm

34 inches to mm:

34 inches = 34 * 25.4 mm = 863.6 mm

36 inches to mm:

36 inches = 1 yard = 36 * 25.4 mm = 914.4 mm

Inches (in) to Millimeters (mm) Conversion Table

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

Inches (in)
Millimeters (mm)
0.1  2.54
0.25  6.35
0.5  12.7
1  25.4
2  50.8
3  76.2
5  127
10  254
50  1270
100  2540


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

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A Brief Intro to Inches and Millimeters

The measurements of length, specifically millimeters and inches, serve as the backbone for a myriad of applications, ranging from intricate engineering designs to daily tasks.

Both units have undergone extensive evolution, embodying the cultural, scientific, and technological strides of their respective origins.

The Genesis and Development of Meters and Millimeters

Originating in the fervor of the French Revolution, the metric system proposed a uniform approach to measurements with the meter at its core. This revolutionary system sought to eliminate the chaotic array of measurements that prevailed by introducing a standard based on natural constants.

In 1791, the meter was ambitiously defined by the French Academy of Sciences as the ten-millionth part of the quarter meridian, the distance from the equator to the North Pole through Paris.

The concrete realization of this concept came in 1799 with the crafting of a platinum standard meter bar. This act of standardization was pivotal, marking a departure from the diverse local measurements that were commonplace.

The millimeter, conceived as one-thousandth of a meter, is seamlessly integrated into this new decimal system, underscoring the system's elegance and rationality.

The adoption of the metric system, with the millimeter as a key component, expanded gradually, bolstered by the 1875 Metre Convention, which sought international uniformity in measurements.

The Intricate Tapestry of the Inch and Its Unification

The inch's journey is storied and multifaceted, woven from the measurement practices of various civilizations, including the Anglo-Saxons and Romans.

Deriving from "uncia," the Latin term for "one-twelfth," the inch historically represented the length of a thumb's width, a measure deeply ingrained in the Roman measurement system as one-twelfth of a foot.

This unit's length varied significantly across different regions and epochs, reflective of the myriad local customs and measures. The advent of the Industrial Revolution underscored the dire need for a standardized measurement system, as precision became paramount in manufacturing and technological advancements.

A landmark in the inch's history was the 1959 agreement between the United States and Commonwealth nations, which crystallized the inch as precisely 25.4 millimeters. This accord not only standardized the inch but also symbolically bridged it with the metric system, facilitating interoperability and precision in global measurements.