The International System of Units (Système International d’Unités), abbreviation SI, is based on the seven main units established by the General Conference on Weights and Measures (Conférence générale des poids et mesures, CGPM): metre, kilogram, second, ampere, kelvin, mole and candela.

The definitions of the units are based on the fixed numerical values of fundamental constants. The fixed values allow for the accurate expression of the numerical values of the main units.

The uniform system of measurement units plays a significant role in our everyday life. Before the creation of the uniform system, various different systems were used in the world. Length was measured in feet, yards and miles, while weight was measured in pounds, ounces and taels. The uniform system of units and the established definitions of units ensure that measurements at different places in the world are mutually comparable.

Today, many countries use the uniform international system of units. Using the system facilitates communication between different countries. People no longer need to constantly convert units and the units of the uniform system have the same value all across the world. The use of the SI system standardises all the measurements. This enables people to exchange data across the world without any confusion.

Have a look at a table explaining the SI units here.