## Why Standard Units of Measurement are Needed?

What if there are no standard units of measurement? Imagine a situation, when a man wants to buy a red coloured shirt, so he goes to a store. The shopkeeper speaks only English. The man says, “Ureed qameesan ahmar allawn”. The shopkeeper says, “What?!” The man asked for a red coloured shirt, but he said it in Arabic. Obviously, the shopkeeper couldn’t understand anything since it was not a standard language.

Similarly, there are many systems and units in place for measuring different quantities like length, area, mass, volume and other things. For example, an acre is a common way of representing area measurement in India. One acre is around 4046 square meters if you look at the metric system.

## What is the International System of Units?

Traditionally, people didn’t have any measuring devices to calculate standard measurement units. To tackle this problem they came up with different innovative ways of measuring with the tools available at hand. For example, they used a foot as a measurement of length. 1 foot is around 0.3 meters which is 30 cm. Another measurement our ancestors used for length was a league. One league was the amount of distance covered by a person when we walked for an hour. This unit, however, is no longer in use.

To tackle this problem of different systems of measurement (just like the different languages), a system of units called the **International System of Units** was established and has been adopted by most developed and developing countries. Although this has been established and adopted across major fields like science and technology and government operations, normally people still refer to their customary or traditional units. For example, in the United States of America people even now refer to lengths in terms of inches and feet instead of centimetres and meters.

**International System of Units**

The International System of Units or SI units defines standard measurement units for measurement of all physical quantities. Examples of these base quantities are given below.

- Length – meter (m)
- Mass – kilogram (kg)
- Time – second (s)
- Electric Current – Ampere (A)
- Temperature – Kelvin (K)
- Amount of Substance – mole (mol)
- Luminous Intensity – candela (cd)

Apart from the base units, there are SI units of derived units. These are called as such because their value is determined based on one or more base units. Some examples are given below.

- Frequency – Hertz (Hz); 1 Hz = 1 s
^{-1} - Power – Watt (W); 1 W = 1 kg·m
^{2}s^{−3}

Stay tuned with BYJU’S to learn more about the International System of Units, various derivations and laws in Physics and much more.