John travelled 4 km from his house to Sam's house. Sam travelled 2.5 miles to John's house from his house with the same route taken by John. Wait! If John and Sam are travelling on the same route, shouldn't the distance be the same? In fact, both the distances are the same. But as the units are different, it can be confusing at times. Both the units are based on different systems of measurement called Metric and imperial units.
Here, we will understand the Metric and Imperial units of measurement and learn how to make conversions.
Metric and imperial units definition
Over the years in all aspects of life, there has always been a call to determine performance. In order to achieve this, several systems of measurement have been developed to measure different physical quantities and other phenomena. Some of the most used measurement systems are the Metric system and the Imperial system.
The metric unit system, also known as the SI unit is the most followed system in the world. This measuring system measures quantities like distance, height, and volume in terms of metre, gram, litre.
The metric system is the measuring system to measure physical quantities based on the decimal system and powers of \(10\).
Some of the units in the metric system include centimetre, decalitre, kilogram, square metre, and so on.
The other system of measurement which is followed by some countries is the Imperial system. It is also known as the British imperial system as it originated in Britain. This system of measurement uses units in terms of inches, pounds, gallons, etc.
The system of measurement which includes inch, mile, and pounds to calculate quantities and deals with irregular units is called the Imperial system.
Let's understand the units and the conversion of both systems in detail.
Imperial and metric units of measurement
Imperial and metric unit of measurement, both measure different quantities like distance, volume, and weight, but uses different measuring units. The metric system depends on the decimal system, while the imperial system has more irregularity between the units.
Metric system of measurement
The metric system of measurement is a base \(10\) system of units built on a collection of base units. This translates to a system where each unit is a combination of a base unit and a prefix, and each succeeding unit is \(10\) times larger than the previous one. And all the values are in the reference to the base unit.
Here in the table, the prefix with its value is mentioned to make it easier to understand.
| Prefix | Symbol | Value | Exponent |
| kilo | k | \(1000\) | \(10^{3}\) |
| hecto | h | \(100\) | \(10^{2}\) |
| deca | da | \(10\) | \(10^{1}\) |
| Base unit | | \(1\) | \(10^{0}\) |
| deci | d | \(\frac{1}{10}\) | \(10^{-1}\) |
| centi | c | \(\frac{1}{100}\) | \(10^{-2}\) |
| milli | m | \(\frac{1}{1000}\) | \(10^{-3}\) |
The prefix values mentioned above work for all the three measuring units of metre (for length), gram (for mass), and litre (for volume). To convert from one prefix to another, either we can multiply/divide or change the decimal point.
If the conversion unit is smaller, then multiply it with the appropriate power of \(10\). Or if the conversion unit is larger, then divide it with the appropriate power of \(10\).
If the prefix of conversion value is smaller, then shift the decimal point to the right side for each power of \(10\). And if the prefix is larger, then shift the decimal point to the left side for each power of \(10\).
Imperial system of measurement
Imperial units take their origin from the UK, Great Britain more precisely. According to the 1824 and 1878 Weights and Measures Act, formal terms of units were used in measurement and generalised in their application over other units of measurement. Some imperial units are pints, feet, inches, ounce, grain, mile, acre, etc.
The imperial system does not have any specific pattern, but has some specific units for conversions. Let us see these conversion units in the form of the table below.
| Quantity | Conversion units |
| Length | \[1 \, ft = 12 \, inch\]\[1 \, yard = 3 \, ft\]\[1 \, mile = 1760 \, yards\] |
| Mass | \[1 \, lb = 16 \, oz\]\[1 \, ton = 2000 \, lbs\] |
| Volume | \[1 \, gallon = 4 \, quarts\]\[1 \, quart = 2 \, pints\]\[1 \, pint = 2 \, cups\] |
To carry out the conversion between different imperial units, we need to multiply/divide as per the given conversion in the above table.
Metric and imperial units conversion
We can also make conversions from the metric system to the imperial system. For that, imperial units have a particular calculated conversion unit in the metric system. We will see these conversion units as per the quantity in the form of tables below.
Length
Length is used to measure any type of distance or size. For example, the size of the book in terms of thickness and length, or distance between two places.
| Metric to Imperial | Imperial to Metric |
| \[1 \, cm = 0.39 \,inch\] | \[1 \, inch = 2.54 \,cm\] |
| \[1 \, m = 3.28 \, ft\] | \[1 \, ft = 0.30 \,m\] |
| \[1 \, m = 1.09 \,yard\] | \[1 \, yard = 0.91 \,m\] |
| \[1 \, km = 0.62 \,mile\] | \[1 \, mile = 1.61 \,km\] |
Mass
Mass is the unit measure for finding the weight of any object. Example - the weight of our body, the quantity of vegetables in weight.
| Metric to Imperial | Imperial to Metric |
| \[1 \, mg = 0.015 \,grain\] | \[1 \, grain = 64.80 \,mg\] |
| \[1 \, gram = 0.035 \,oz\] | \[1 \, oz = 28.35 \,gram\] |
| \[1 \, kg = 2.20 \,lb\] | \[1 \, lb = 0.45 \,kg\] |
| \[1 \, tonne = 0.98 \,ton \,(UK)\] | \[1 \, ton(UK) = 1.02 \,tonne\] |
Volume
The capacity of any object that can hold the amount of any liquid is measured in volume. Examples of volume can be juice in a bottle, or water in a jug.
| Metric to Imperial | Imperial to Metric |
| \[1 \, ml = 0.035 \,fl \,oz\] | \[1 \, fl \,oz = 28.41 \,ml\] |
| \[1 \, litre = 1.76 \,pint\] | \[1 \, pint = 0.57 \,litres\] |
| \[1 \, m^{3} = 219.97 \,gallons\] | \[1 \, gallon = 4.55 \,litres\] |
Temperature
Temperature determines the hotness or coldness of any object or body. And it is derived in terms of degree. The Celsius scale is used for the metric system and the Fahrenheit scale is used for the imperial system to calculate the temperature.
Conversion from Celsius to Fahrenheit is done by first multiplying the given value by \(\frac{9}{5}\), and then adding 32 to it.
Conversion from Fahrenheit to Celsius is done by first subtracting the given value by 32, and then multiplying \(\frac{5}{9}\) to it.
Difference between imperial and metric units
Now that we have an understanding of both systems, let us take a look at the main difference between imperial and metric units.
| Imperial units | Metric units |
| Imperial unit is the system of measurement with some specific conversion values. | Metric unit is the system of measurement based on the decimal system. |
| Imperial units are also known as British imperial system. | Metric units are well known as Système international (SI) units. |
| There is no specific pattern between the units | All the units are the powers of \(10\). |
| Examples of imperial units are foot, inch, yard, gallon, pint, ounce, pound. | Examples of metric units are metre, kilometre, gram, decigram, litres. |
Metric and imperial units examples
Here are some solved metric and imperial units examples.
Identify and state the measurement system for the given quantities.
- Distance between two places in \(50 \,km\).
- Max is \(6 \,feet \,2 \,inches\) tall.
- The weight of a cargo ship is \(199000 \,tonnes\).
- The volume of water in a jug is \(5.2 \,pints\).
- Today the temperature outside is \( 806°F\).
Solution:
The system of measurement used for the above statements is as follows:
- Metric system
- Imperial system
- Metric system
- Imperial system
- Imperial system
Calculate the following conversions.
- Convert \(30 \,km\) to \(metres\).
- How many \(quarts\) does \(110 \,pints\) makes?
Solution:
1. Here we are given \(30 \,km\) and we need to convert it to \(metres\). From the above discussion we know that both the units are of metric system. So, we will look at the conversion table of metric system.
The km is larger unit than metre unit. As per the conversion method we will multiply it with the appropriate power of \(10\).
\[\begin{align}\Rightarrow 30 \,km &= 30\times 10^{3} \\& = 30,000 \,metres \\\end{align}\]
2. Here both the units are of the imperial system, so we will refer to the corresponding conversion table. So, we see that,
\[1 \, quart = 2 \, pints\]
\[\begin{align}\Rightarrow 1 \,pint & = \frac{1}{2} quarts \\& = \frac{1}{2} \times 110 \\& =55 \,quarts\end{align}\]
A bag of flour weighs \(6 \,kg\). How much is the weight in terms of ounces?
Solution:
We are given \(6 \,kg\) (metric system). And we need to convert it into ounces (imperial system). Now, from the conversion table we know that \(1 \, kg = 2.20 \,lb\). Using this conversion value, we will first convert it in terms of pound (lb) and then convert it into ounces.
\[\Rightarrow 1 \, kg = 2.20 \,lb\]
\[\begin{align}\Rightarrow 6 \, kg & = 2.20\times 6 \,lb \\& = 13.2 \,lbs\end{align}\]
Now, \(1 \, lb = 16 \, oz\), then,
\[\begin{align}\Rightarrow 13.2 \, lbs & = 16\times 13.2 \,oz \\& = 211.2 \,oz\end{align}\]
Hence, the bag of flour weighs \(211.2 \,oz\).
Metric and imperial units - Key takeaways
- The metric system is the measuring system to measure physical quantities based on the decimal system and powers of \(10\).
- The system of measurement which includes inch, mile, and pounds to calculate quantities and deals with irregular units is called the Imperial system.
- The units in the metric system include kilometre, gram, decalitre, Celsius, and so on. While, the units of imperial systems are yards, inches, pounds, gallons, pints, Fahrenheit, and so on.
- Imperial and metric unit of measurement, both measure different quantities like distance, volume, and weight, but uses different measuring units.
- The metric system depends on the decimal system, while the imperial system has more irregularity between the units.
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