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CODATA Recommended Values of the Fundamental Physical Constants: 2018



Eite Tiesinga, Peter J. Mohr, David B. Newell, Barry N. Taylor


We report the 2018 self-consistent values of constants and conversion factors of physics and chemistry recommended by the Committee on Data of the International Science Council (CODATA). The recommended values can also be found at The values are based on a least-squares adjustment that takes into account all theoretical and experimental data available through 31 December 2018. A discussion of the major improvements as well as inconsistencies within the data is given. The former includes a decrease in the uncertainty of the dimensionless fine-structure constant and a nearly two orders of magnitude improvement of parti- cle masses expressed in units of kg due to the transition to the revised International System of Units (SI) with an exact value for the Planck constant. Further, because the elementary charge, Boltzmann constant, and Avogadro constant also have exact values in the revised SI, many other constants are either exact or have significantly reduced uncertainties. Inconsistencies remain for the gravitational constant and the muon magnetic-moment anomaly. The proton charge radius puzzle has been partially resolved by improved measurements of hydrogen energy levels.
Journal of Physical and Chemical Reference Data (Pending Approval)


fundamental constant, precision measurements, fine-structure constant


Tiesinga, E. , Mohr, P. , Newell, D. and Taylor, B. (2022), CODATA Recommended Values of the Fundamental Physical Constants: 2018, Journal of Physical and Chemical Reference Data (Pending Approval), [online],, (Accessed April 19, 2024)
Created January 10, 2022, Updated November 29, 2022