SI Base Units
The seven defined units of the International System from which every other measurement unit is derived.
Unit
Various
In depth
The seven are the metre, kilogram, second, ampere, kelvin, mole and candela. Since 2019 each is defined by fixing the numerical value of a fundamental constant — the Planck constant for the kilogram, the Avogadro constant for the mole — rather than by a physical artefact, making them reproducible in any laboratory.
Examples in the real world
Amount of substance is measured in moles, temperature in kelvin, and mass in kilograms; the derived unit of pressure, the pascal, equals kg·m⁻¹·s⁻².