SIbasenheterna

SIbasenheterna, or the SI base units, are the seven foundational units of the International System of Units (SI). They are the reference quantities from which all other SI units are derived, and their definitions are fixed by invariant physical constants rather than artefacts. The term is used in Swedish-language sources to denote the base units in the SI.

The seven base units are the metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd). Since 2019, each base unit has been defined by a fixed numerical value of a fundamental constant: the metre by the speed of light in vacuum (c = 299,792,458 m/s); the kilogram by the Planck constant (h = 6.62607015×10^-34 J s); the second by the cesium-133 transition (9,192,631,770 cycles); the ampere by the elementary charge (e = 1.602176634×10^-19 C); the kelvin by the Boltzmann constant (k = 1.380649×10^-23 J K^-1); the mole by Avogadro's constant (NA = 6.02214076×10^23 mol^-1); and the candela by luminous efficacy for a monochromatic source at 540 THz with radiant intensity 1/683 W per steradian.

These definitions anchor measurements in universal constants, providing precision and reproducibility across science, industry, and commerce. The SI base units are maintained by the International Bureau of Weights and Measures (BIPM) and implemented worldwide through national metrology institutes, ensuring traceability and consistency in measurements globally.