The kilogram, symbol \(\text{kg}\), is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10
−34 when expressed in the unit J s, which is equal to kg m
2 s
-1, where the metre and the second are defined in terms of
c and Δ
νCs.
Source:
BIPM, The International System of Units, SI Brochure, 9th ed. (2019), p. 131 (https://www.bipm.org/en/publications/si-brochure/)