Knowing how to measure quantities, values, time, distance, percentage, and accuracy is crucial to making decisions based on measurement results. It is not wrong to say modern society could not exist without measurement. From shopping to buying a small quantity, measurement is used everywhere. 

Various measurement units, methods, and conversions help calculate the commodities or units within no time. Unfortunately, some students and even adults neglect the importance of measurement when they get used to its fundamentals. Every quantity in the world can be measured with the help of seven International Systems of Units, which are also the fundamental units of measurement. These are: 

Quantity  Unit  Symbol 
Length  meter  m
Time  second  sec
Amount of substance  mole  mol
Electric current  ampere  amp
Temperature  kelvin  K
Luminous intensity  candela  cd
Mass  Kilogram  kg

However, other than the International System of Units, the Imperial system is also used in many countries, such as the United States of America, Myanmar, Liberia, and many more. The units in the Imperial system, also known as the British Imperial System, are as follows: 

Weight  Capacity  Length  Area  Volume 
Short ton Gallon  Nautical mile  Square mile  Cubic yard 
Long ton Quart  Mile  Acre  Cubic foot 
Hundredweight  Pint  Furlong  Square rod  Cubic inch 
Short hundredweight Gill  Rod  Square yard  Acre-foot 
Long hundredweight Fluid ounce  Fathom  Square foot  Board foot 
Pound  Fluid dram  Yard  Square inch  Cord 
Ounce  Minim  Foot 
Dram  Bushel  Inch 
Grain  Peck 
Stone 

Length: The most used measuring unit in daily life 

How do you measure how long you have run on a treadmill? Or how long have you jogged around a park in the early morning? How do you measure the distance between your home from your friends’ homes? This is when length comes to the rescue. Length is commonly assumed as the largest dimension of any object among breadth, length, and height. However, it might not always be true when measuring an object in real life. 

There are several units to measure length. A few of them are meter, kilometer, inch, millimeter, centimeter, yard, mile, nautical mile, foot, rod, furlong, and fathom. To compare one or more objects having different length units, there is a need to convert them into one unit for ease of calculation. So, how do we do it? 

 Learning to convert one unit to another  

For basic conversions in the meter scale, remember the diagram shown below. To convert from millimeter to meter, we need to divide the given value in multiples of ten. And to convert the meter to the millimeter, we need to multiply the given value by multiples of ten. 

Here are a few conversions equivalents that will help anyone to convert units between Imperial and SI:

Imperial  SI 
1 mile  1.6 km 
3.3 feet  1 meter
1 inch  2.54 centimeter 
1 gallon  3.79 liters 
1 fluid ounce  30 ml 
1.102 net, or short tons (2000 pounds)  1 metric ton (1000 kg)
2.2 pounds  1 kilogram 
1 ounce  28.35 grams 

How to convert millimeters(mm) to inches? 

Before learning to convert mm to inches, let us know what millimeters and inches are. 

In 1983, the meter was defined by the 17th Conference of Weights and Measures as ‘the length of the path traveled by light in vacuum during a time interval of 1/299792458 of a second.’ Since the meter is the base unit of length, let us define millimeters in terms of meters. 

A millimeter is a unit of length in the SI unit system, equivalent to 1/1000 of a meter. 

A corresponding unit area is one square millimeter, and the corresponding unit volume will be a cubic millimeter. For area, it is represented as mm2, and for volume, it will be represented as mm3

On the other hand, an inch is a unit of length mainly used in the Imperial system and the US customary measurement system. It is represented by “ symbol. For example, 4” is pronounced as 4 inches. One must make sure not to use single quotes. A single quote represents another unit, known as afoot. Moreover, an inch is represented as 1/12 of a foot and 1/36 of a yard. 

 So, how do we convert mm to inches? Students should remember the given conversion:

1 mm = 0.039370 inch

Remembering this conversion rate will assist in speeding up the calculation. But for fundamental clarity, let’s see how this conversion has been done. 

We know, 1 centimeter = 10 millimeter      (1)

Also, 1 inch = 2.54 cm 

This gives, 1 cm = 1/2.54 inch        (2) 

Equating both the equations, we get, 

10 mm = 1/2.54 inch

Therefore, 1 mm = 1/ (2.54 x 10) inch 

1 mm = 0.039370 inch

 Let us understand another method to convert this rate. 

Using unitary method in fractional form, 1 mm can be written as:

1 cm/10 mm x 1 inch/2.54 cm = 1 

Canceling these units, we get 1mm = 0.039370 inches. We can use this conversion method to convert any unit. 

So, if anyone asks – how many inches are there in a millimeter. The answer will be – 1 millimeter has 0.039370 inches. 

And for – how many millimeters are there in an inch. The answer will be – 1 inch has 25.4 millimeters. As, 1 inch = 1/0.039370 mm = 25.4 mm 

Applications of measuring units 

  • The same units of measurement help to understand architectural drawings, no matter who has made them. Moreover, if the units are standardized, a layperson can read them.
  • Standardized units help in global trading. For instance, if one country has to buy goods from another, standardized conversion of units will help in the ease of trade. 
  • Measuring units are very helpful while doing science experiments. Imagine if the units were not the same in your textbooks. For example, a student would pour diluted sulphuric acid more than the other, leading to an accident. Therefore, having standard units is necessary. 

Learning mm to inch by examples

Example 1: Convert 6 mm to inches. 

Solution: We know that 1 mm = 0.039370 inch

Therefore, 6 mm will be, 6 x 0.039370 inch 

6 mm = 0.23622 in

Example 2: How to convert 10 mm to inches? 

Solution: We are well-acquainted with the conversion as: 1 mm = 0.039370 inch

Using unitary method by fraction, we get, 

1 cm/10 mm x 1 inch/2.54 cm = 10 

Therefore, 10 mm = 0.39370 in

Example 3: Convert 40 mm to inches. 

Solution: We know, that 1 mm = 0.039370 inch

Therefore, 40 mm will be, 40 x 0.039370 inch 

40 mm = 1.5748 in

Example 4: How to convert 50 mm to inches?

Solution: Using unitary method by fraction, we get, 

1 cm/10 mm x 1 inch/2.54 cm = 50

Therefore, 50 mm = 1.9685 in

Given below is the conversion table that can be memorized for speedy calculations:

Millimeters (mm) Inches (“) Inches (“) (fraction) 
0.01 mm 0.0004 ″ 0 ″
0.1 mm 0.0039 ″ 0 ″
1 mm 0.0394 ″ 3/64 ″
2 mm 0.0787 ″ 5/64 ″
3 mm 0.1181 ″ 1/8 ″
4 mm 0.1575 ″ 5/32 ″
5 mm 0.1969 ″ 13/64 ″
6 mm 0.2362 ″ 15/64 ″
7 mm 0.2756 ″ 9/32 ″
8 mm 0.3150 ″ 5/16 ″
9 mm 0.3543 ″ 23/64 ″
10 mm 0.3937 ″ 25/64 ″
20 mm 0.7874 ″ 25/32 ″
30 mm 1.1811 ″ 1 3/16 ″
40 mm 1.5784 ″ 1 37/64 ″
50 mm 1.9685 ″ 1 31/32 ″
60 mm 2.3622 ″ 2 23/64 ″
70 mm 2.7559 ″ 2 3/4 ″
80 mm 3.1496 ″ 3 5/32 ″
90 mm 3.5433 ″ 3 35/64 ″
100 mm 3.9370 ″ 3 15/16 ″