Inches To Millimeters Conversion

1 in = 25.4 mm

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The Ratio Between Inches and Millimeters

Visualising the relationship between inches and millimeters makes it easier to convert between the two. Inches are used to establish the baseline ruler and the millimeters ruler is sized in relation to that baseline.

conversion scale showing the ratio between inches and the equivalent number of millimeters

How to convert inches to millimeters (in to mm)

To convert inches to millimeters (inch to mm), you can multiply the number of inches by 25.4. This is the conversion factor for inches to millimeters. It is derived from the fact that there are 12 inches in a foot and 304.8 millimeters in a foot. Here is the mathematical equation for calculating millimeters in inches: mm = in × 25.4.

Example Conversion

Let's take a look at an example. The step-by-step process to convert 5 inches to millimeters is:

Understand the conversion formula: mm = in × 25.4
Substitute the required value. In this case we substitute 5 for in so the formula becomes: mm = 5 × 25.4
Calculate the result using the provided values. In our example the result is: 5 × 25.4 = 127 mm

In summary, 5 inches is equal to 127 millimeters.

Converting millimeters to inches

In order to convert the other way around i.e. millimeters to inches, you would use the following formula: in = mm ÷ 25.4. To convert millimeters to inches first substitute the millimeter value into the above formula, and then execute the calculation. If we wanted to calculate 1 millimeter in inches we follow these steps:

in = mm ÷ 25.4

in = 1 ÷ 25.4

in = 0.0393700787401574803149606299213

Or in other words, 1 millimeter is equal to 0.0393700787401574803149606299213 inches.

Conversion Unit Definitions

What is a Inch?

The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to 1/36 yard or 1/12 of a foot. Derived from the Roman uncia ("twelfth"), the word inch is also sometimes used to translate similar units in other measurement systems, usually understood as deriving from the width of the human thumb.

Standards for the exact length of an inch have varied in the past, but since the adoption of the international yard during the 1950s and 1960s the inch has been based on the metric system and defined as exactly 25.4 mm.

The inch is a commonly used customary unit of length in the United States, Canada, and the United Kingdom. It is also used in Japan for electronic parts, especially display screens. In most of continental Europe, the inch is also used informally as a measure for display screens. For the United Kingdom, guidance on public sector use states that, since 1 October 1995, without time limit, the inch (along with the foot) is to be used as a primary unit for road signs and related measurements of distance (with the possible exception of clearance heights and widths) and may continue to be used as a secondary or supplementary indication following a metric measurement for other purposes.

Here are some additional details about the inch:

Origin: The inch has its roots in the ancient Roman measurement system. The word "inch" is derived from the Latin word "uncia," which means one-twelfth part.
Imperial and US Customary Systems: The inch is a fundamental unit in both the Imperial system and the United States Customary system. These systems of measurement are primarily used in the United States and other countries that have historical ties to the British Empire.
Length Conversion: As mentioned earlier, one inch is equal to exactly 1/12th of a foot. In the metric system, it is approximately equal to 2.54 centimeters. Conversely, one foot is equal to 12 inches.
Subdivisions: The inch can be further divided into smaller units to measure even finer lengths. Common subdivisions include:
- Half-inch (1/2 inch): Equal to 0.5 inches or approximately 1.27 centimeters.
- Quarter-inch (1/4 inch): Equal to 0.25 inches or approximately 0.635 centimeters.
- Eighth-inch (1/8 inch): Equal to 0.125 inches or approximately 0.318 centimeters.
- Sixteenth-inch (1/16 inch): Equal to 0.0625 inches or approximately 0.159 centimeters.
- Thirty-second inch (1/32 inch): Equal to 0.03125 inches or approximately 0.079 centimeters.
Common Uses: The inch is commonly used to measure various objects, particularly in fields like construction, engineering, manufacturing, and carpentry. It is often used to measure dimensions of building materials, tools, furniture, and other everyday items.
Symbol: The symbol for inch is a double prime ("). For example, a measurement of 5 inches would be written as 5".
International Usage: While the metric system (based on the meter) is widely adopted worldwide, the inch is still used in certain countries, such as the United States, Canada, and the United Kingdom. However, it is worth noting that many industries and scientific disciplines have transitioned to using metric measurements for international consistency.

What is a Millimeter?

The millimeter is a unit of length in the metric system. It is defined as one-thousandth of a meter or 0.001 meters. The millimeter is primarily used to measure very small distances or dimensions.

Here are some additional details about the millimeter:

Metric System: The millimeter is part of the metric system, which is widely used around the world. The metric system provides a decimal-based system of measurement that offers simplicity, consistency, and ease of conversion across different scientific, industrial, and everyday applications.
Length Conversion: One millimeter is equal to 0.001 meters or 0.1 centimeters. Conversely, one meter is equal to 1,000 millimeters.
Common Uses: The millimeter is often used in various fields and applications where precision is required. It is commonly used in fields such as engineering, manufacturing, construction, medicine, and technology. The millimeter is well-suited for measuring small objects, thicknesses, clearances, and other precise dimensions.
Symbol: The symbol for millimeter is "mm". For example, a measurement of 5 millimeters would be written as 5 mm.
Subdivisions: The millimeter itself is a small unit of measurement, but it can be further divided into even smaller units for more precise measurements. For example, one millimeter is equal to 1,000 micrometers (µm) or one million nanometers (nm).
International Usage: The millimeter is widely accepted and used internationally as a standard unit of measurement. It is embraced in most countries that have adopted the metric system. Its universal usage promotes consistency and facilitates communication, collaboration, and compatibility across various fields and regions.
Advantages: The millimeter offers a high level of accuracy and precision for measuring small lengths or dimensions. Its decimal nature allows for easy conversion to other metric units and simplifies calculations involving measurements.