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 Convert mm to inches: A Comprehensive Guide with Examples

In the world of measurements, understanding different units and their conversions is crucial for various fields, including engineering, construction, manufacturing, and even everyday tasks. Two commonly used units for measuring length are millimetres (mm) and inches. 

Whether you’re a professional or a DIY enthusiast, being able to convert between these units seamlessly can save you time and prevent costly mistakes. In this comprehensive guide, we’ll delve into the details of converting mm to inches and provide you with practical examples to reinforce your understanding.

Part1. What is mm (Millimeter)?

What is mm (Millimeter)?

A millimetre (mm) is a metric unit of length equal to one-thousandth of a meter, the fundamental unit of length in the International System of Units (SI). It is a small yet precise unit, widely used in scientific measurements, engineering drawings, and various other applications.

#1. Uses of Millimeter

Millimeters are commonly employed in numerous areas, including:

  • Measuring tumour sizes in medical imaging
  • Determining wavelengths in optics and telecommunications
  • Specifying paper and material thicknesses
  • Gauging precise dimensions in manufacturing and engineering

Part2. What are Inches?

An inch is a unit of length in the imperial and US customary systems of measurement. It is defined as one-twelfth of a foot or one-thirty-sixth of a yard. The term “inch” is derived from the Latin word “uncia,” meaning “one-twelfth.”

#1. Uses of Inches

Inches are widely used in various contexts, including:

  • Measuring screen sizes of electronic devices
  • Specifying radial wheel sizes in the automotive industry
  • Determining fabric and cloth dimensions in the textile industry

Part 3. mm to inches conversion Formula and Examples

To convert millimetres (mm) to inches, you can use the following mm to inches formula:

inches = mm × 0.0393701

This formula is derived from the fact that 1 inch is equal to 25.4 millimetres.


1. Convert 10 mm to inches: 

Step 1: Substitute the value in the formula inches = 10 mm × 0.0393701

Step 2: Calculate the result inches = 0.393701 inches

2. Convert 75 mm to inches: 

Step 1: Substitute the value in the formula inches = 75 mm × 0.0393701 

Step 2: Calculate the result inches = 2.952757 inches

3. Convert 200 mm to inches

Step 1: Substitute the value in the formula inches = 200 mm × 0.0393701 

Step 2: Calculate the result inches = 7.87402 inches 

#Steps for Converting mm to inches: 

  1. Identify the value in millimetres (mm) that you want to convert to inches. 
  2. Substitute the value in the formula: inches = mm × 0.0393701 
  3. Perform the multiplication to calculate the equivalent value in inches. 
  4. The result will be the converted value from millimetres to inches.

Remember, the conversion factor (0.0393701) is derived from the fact that 1 inch is equal to 25.4 millimetres. This factor allows you to convert between the two units accurately

Part 4. How to Convert mm to inches & Inches to mm?

The most straightforward way to convert millimetres (mm) to inches (in) is by using the mm to inches conversion factor of 0.0393701. This value comes from the fact that 1 inch is equal to 25.4 mm.

To convert mm to inches, follow these steps:

  • Identify the length in millimetres you want to convert to inches.
  • Multiply the mm value by the conversion factor 0.0393701.

The formula is:

inches = mm × 0.0393701

For example, to convert 50 mm to inches:

inches = 50 × 0.0393701 = 1.96851 inches

To convert a different mm value, simply substitute it into the formula and multiply by 0.0393701.

It’s also useful to know some common mm-to-inches conversions:

10 mm = 0.393701 inches

25 mm = 0.984252 inches

100 mm = 3.93701 inches

For greater precision, the inches result can be expressed as a fraction by rounding appropriately. Most conversions round to the nearest 1/64 of an inch.

The reverse conversion from inches to mm uses:

mm = inches × 25.4

Following this simple multiplication method allows you to easily convert between the mm and inch units when working across different measurement systems.

#mm to inches Conversion Table

Here’s a handy mm-to-inches conversion table to quickly convert common millimetre values to inches:

Millimetres (mm)Inches (in)
1 mm0.0394 in
5 mm0.1969 in
10 mm0.3937 in
25 mm0.9843 in
50 mm1.9685 in
100 mm3.9370 in
500 mm19.6850 in
1000 mm39.3701 in

If you’re looking to deepen your understanding of measurement conversions and gain a competitive edge, consider enrolling in WuKong Math: Unit Conversion Mastery. This comprehensive program is designed to equip you with the knowledge and skills necessary to convert between different units of measurement, from millimetres to inches. 

Master the mm to inches conversion formula, learn to use an mm to inches chart or ruler, and even explore converting mm to feet and inches fractions. Don’t miss this opportunity to elevate your mathematical prowess in unit conversions and unlock new possibilities in your academic or professional journey.

Part5. Difference between mm and Inches

Difference between mm and Inches

Although both millimetres and inches are units of length, they belong to different measurement systems with distinct characteristics:

  • Millimetres are part of the metric system, which is based on decimal units and follows a consistent pattern of prefixes (e.g., centimetre, kilometre).
  • Inches belong to the imperial system, which is based on a different set of units and conversions.
  • The metric system, including millimetres, is used in most countries worldwide, while the imperial system is primarily used in the United States and a few other countries.
  • Millimetres are smaller units than inches, with 1 inch being approximately equal to 25.4 millimetres.

#1. Advantages of Metric System

The metric system, which includes millimetres, offers several advantages over the imperial system:

  • It is a decimal-based system, making conversions between units much easier and more intuitive.
  • It follows a consistent pattern of prefixes, allowing for a more logical understanding of units.
  • The metric system is used internationally, facilitating communication and collaboration across borders.
  • Scientific and technical fields heavily rely on the metric system, ensuring standardization and accuracy.

FAQs about mm to inches

Q1. How do I convert mm to inches manually?

To convert millimetres to inches manually, you can use the formula: inches = mm × 0.0393701. For example, if you want to convert 50 mm to inches, you would calculate 50 × 0.0393701 = 1.9685 inches.

Q2. How many mm are in 1 inch?

There are approximately 25.4 millimetres in 1 inch. This conversion factor is derived from the fact that 1 inch is equal to 1/36 of a yard, and 1 yard is 0.9144 meters or 914.4 millimetres.

Q3.  What are some common uses of mm measurements?

Millimeters are commonly used in various applications, including:

  • Measuring the size of electronic components and circuits
  • Specifying the thickness of materials like paper, plastic, and metal sheets
  • Determining the diameter of screws, bolts, and other fasteners
  • Gauging the width of hair strands or the size of small objects

Q4. Why is it important to be able to convert units?

Being able to convert between different units is essential for several reasons:

  • It facilitates communication and understanding across different measurement systems.
  • It ensures accuracy when working with international clients or collaborators.
  • It prevents costly mistakes that could arise from misinterpreting measurements.
  • It allows for seamless integration of components or materials from different sources or suppliers.


Converting between millimetres and inches is an essential skill in various fields, enabling effective communication and accurate measurements. By understanding the conversion formulas, utilizing conversion tables, and recognizing the differences between the metric and imperial systems, you can seamlessly navigate between these units. Whether you’re a professional working on international projects, a student tackling complex calculations, or a DIY enthusiast, mastering the conversion from mm to inches will undoubtedly prove invaluable. If you want to konw how to convert cm to inche, If necessary, please check the corresponding article.