Convert inches to mm (2024)

Convert inches to mm (1)

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Please provide values below to convert inch [in] to millimeter [mm], or vice versa.


Definition: An inch (symbol: in) is a unit of length in the imperial and US customary systems of measurement. An inch was defined to be equivalent to exactly 25.4 millimeters in 1959. There are 12 inches in a foot and 36 inches in a yard.

History/origin: The term "inch" was derived from the Latin unit "uncia" which equated to "one-twelfth" of a Roman foot.

There have been a number of different standards for the inch in the past, with the current definition being based on the international yard. One of the earliest definitions of the inch was based on barleycorns, where an inch was equal to the length of three grains of dry, round barley placed end-to-end. Another version of the inch is also believed to have been derived from the width of a human thumb, where the length was obtained from averaging the width of three thumbs: a small, a medium, and a large one.

Current use: The inch is mostly used in the United States, Canada, and the United Kingdom. It is also sometimes used in Japan (as well as other countries) in relation to electronic parts, like the size of display screens.


Definition: A millimeter (symbol: mm) is a unit of length in the International System of Units (SI). It is defined in terms of the meter, as 1/1000 of a meter, or the distance traveled by light in 1/299 792 458 000 of a second.

History/origin: The milli- prefix is one of many metric prefixes. It indicates one thousandth of the base unit, in this case the meter. The definition of the meter has changed over time, the current definition being based on the distance traveled by the speed of light in a given amount of time. The relationship between the meter and the millimeter is constant however. Prior to this definition, the meter was based on the length of a prototype meter bar. In 2019, the meter has been re-defined based on the changes made to the definition of a second.

Inch to Millimeter Conversion Table

Inch [in]Millimeter [mm]
0.01 in0.254 mm
0.1 in2.54 mm
1 in25.4 mm
2 in50.8 mm
3 in76.2 mm
5 in127 mm
10 in254 mm
20 in508 mm
50 in1270 mm
100 in2540 mm
1000 in25400 mm

How to Convert Inch to Millimeter

1 in = 25.4 mm
1 mm = 0.0393700787 in

Example: convert 15 in to mm:
15 in = 15 × 25.4 mm = 381 mm

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Convert inches to mm (2024)


How do you convert inches to mm? ›

To convert inches to mm, you must multiply the unit by 25.4. For instance, if you have to convert 10 inches to mm, you need to multiply 10 with 25.4.

How do you remember mm to inches? ›

Simply divide the number of millimeters by 25.4 to get the equivalent length in inches. Understanding this conversion is critical if you work with measures in the metric system and need to present those measurements in the imperial system.

What is the exact conversion from mm to inches? ›

1 MM = 0.0393701 Inches.

What is the fraction for 1 inch to mm? ›

1 inch = 25.4mm

This represents 2 whole inches plus 3/8 of an inch.

What is the formula for converting mm to inches? ›

Ans : Because one inch is 25.4 millimetres long, the length in inches is millimetres divided by 25.4. The length divided by 25.4 is the formula for converting millimetres to inches.

How many mm is 1⁄8 inch? ›

3.18 mm

How do you calculate in mm? ›

Multiply inches by 2.54 to get centimeters. Multiply inches by 25.4 to get millimeters.

What mm is close to an inch? ›

25mm = almost 1 inch.

What is the scale factor for converting inches to mm? ›

Inches are a measurement in the imperial system, while millimeters are used in the metric system. The standard ratio between these two measurements is 1 inch = 25.4 millimeters.

Is 20 mm the same as 1 inch? ›

Answer: 20 millimeters is equal to approximately 0.7874 inches. Here's how the calculation is done: Given Measurement: 20 mm. Conversion Factor: 1 inch = 25.4 mm.

How many mm is 1 ⁄ 2 inch? ›

Inches to millimeters conversion table
Inches (")Millimeters (mm)
1/2 ″12.7 mm
1 ″25.4 mm
2 ″50.8 mm
3 ″76.2 mm
23 more rows

How many mm is 1 ⁄ 4 inch? ›

To convert 1/4 inch to mm, divide 1 by 4 to convert the fraction to a decimal. Then, multiply that by 25.4 since there are 25.4 millimeters in one inch. That's the formula that our calculator uses to find that 1/4 inch to millimeters is 6.35 mm.

What is the formula for inches to mm? ›

Since there are 25.4 millimeters in one inch, we can calculate the length in millimeters by multiplying the number of inches by 25.4. Thus, the formula to convert inches to millimeters is to multiply the number of inches by 25.4.

What is the fraction for 1 mm to inches? ›

Millimeters to inches conversion table
Millimeters (mm)Inches (") (decimal)Inches (") (fraction)
1 mm0.0394 ″3/64 ″
2 mm0.0787 ″5/64 ″
3 mm0.1181 ″1/8 ″
4 mm0.1575 ″5/32 ″
17 more rows

Is 32 mm equal to 1 inch? ›

Example #3: If an item measures 32mm tall... so 32mm is about 1-1/4" tall.

Is 30 mm equal to 1 inch? ›

Since there are 25.4 millimeters in one inch, the length in inches is equal to millimeters divided by 25.4. Thus, the formula to convert millimeters to inches is the length divided by 25.4.

What is 7 ⁄ 8 inches in mm? ›

How to Convert Inch to mm
Decimal InchesFractional InchesMetric
0.875”7/8”22.23 mm
0.938”15/16”23.83 mm
1”1”2.54 cm
2”2”5.08 cm
21 more rows

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