Grundvallareiningar

Grundvallareiningar, or base units, are the seven fundamental quantities from which all SI units are derived. They form the foundation of the International System of Units (SI) and set the reference points for measurement across science, industry, and commerce. Every SI unit can be expressed in terms of these base units, ensuring consistency and universality.

The seven base units, with their symbols and what they measure, are: metre (m) for length, kilogram (kg) for mass, second (s) for time, ampere (A) for electric current, kelvin (K) for thermodynamic temperature, mole (mol) for amount of substance, and candela (cd) for luminous intensity. In 2019, the definitions of several base units were revised to be anchored to fixed values of fundamental constants. Specifically, the metre is defined by the speed of light in vacuum, the kilogram by the Planck constant, the ampere by the elementary charge, the kelvin by the Boltzmann constant, the mole by the Avogadro constant, and the candela by a specified luminous efficacy. The second remains defined by the frequency of the cesium-133 atom’s ground-state hyperfine transition.

Derived units, such as newton (N), joule (J), and pascal (Pa), are formed from these base units through simple algebraic relationships. For example, force is measured in newtons as kg·m/s^2, energy in joules as kg·m^2/s^2, and pressure in pascals as kg/(m·s^2). The concept of grundvallareiningar is central to metrology, providing a stable, precise framework for measuring the natural world.