Appendix C — Constants

Values from the 2019 revision of the SI, where the constant is exact by definition, and from CODATA otherwise.

Constant	Symbol	Value	Unit	Standard uncertainty	Source
Speed of light in vacuum	\(c\)	\(299792458\)	\(\mathrm{m\,s^{-1}}\)	exact	SI (2019), exact by definition
Planck constant	\(h\)	\(6.62607015 \times 10^{-34}\)	\(\mathrm{J\,s}\)	exact	SI (2019), exact by definition
Reduced Planck constant	\(\hbar\)	\(1.054571817 \times 10^{-34}\)	\(\mathrm{J\,s}\)	exact	h / 2 pi, exact; value truncated to 10 significant digits
Boltzmann constant	\(k_B\)	\(1.380649 \times 10^{-23}\)	\(\mathrm{J\,K^{-1}}\)	exact	SI (2019), exact by definition
Newtonian constant of gravitation	\(G\)	\(6.67430 \times 10^{-11}\)	\(\mathrm{m^3\,kg^{-1}\,s^{-2}}\)	\(1.5 \times 10^{-15}\)	CODATA 2018