Every four years, the Committee on Data for Science and Technology (CODATA) issues recommended values of the fundamental physical constants. The values are determined by a least-squares adjustment, based on all the available theoretical and experimental information. The selection and assessment of data is done under the auspices of the CODATA Task Group on Fundamental Constants.
CODATA Task Group on Fundamental Constants websites at:
Tables of values of the constants:
Wall chart (2014)
Wallet cards (2014)