Metrological dependencies between the different base units of the SI system of units as agreed to on 16 November 2018. This removed the International Prototype of the Kilogram as the definition. The chart shows the fundamental physical constants used to define the base units:

s - the frequency of the cesium hyperfine transition (Δv_Cs) for the second,

m - the speed of light (c) for the metre.

kg - the Planck constant (h) for the kilogram,

A - the elementary electric charge (e) for the ampere,

mol - the Avogadro constant (N_A) for the mole,

K - the Boltzmann constant (k_B) for the kelvin,

cd - the sensitivity of the human eye (K_cd) for the candela,

An arrow ${\displaystyle a\rightarrow b}$ means that ${\displaystyle a}$ is used in the definition of ${\displaystyle b}$.