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The Boltzmann Project



Samuel P. Benz, Joachim Fischer, Bernd Fellmuth, Christof Gaiser, Laurent Pitre, Fernando Sparasci, Lara Risegari, Roberto M. Gavioso, D M. Rippa, Bengt Hallstedt, Jifeng Qu, XiaoJuan Feng, Jianqiang Zhang, David R. White, L Gianfrani, A Castrillo, L Moretti, B Darquie, C Daussy, S Briaudeau, O Kozlova, J J. Segovia, M C. Martin, D del Campo, Michael R. Moldover


The International Committee for Weights and Measures (CIPM), at its meeting in October 2017 followed the recommendation of the Consultative Committee for Units (CCU) on the redefinition of the kilogram, ampere, kelvin and mole. For the redefinition of the kelvin the Boltzmann constant will be fixed with the numerical value 1.380 649x10-23 JK^-1. The relative standard uncertainty to be transferred to the thermodynamic temperature value of the triple point of water will be 3.7x10^-7, corresponding to an uncertainty in temperature of 0.10 mK, sufficiently low for all practical purposes. With the redefinition of the kelvin the broad research activities of the temperature community on the determination of the Boltzmann constant have been very successfully completed. In the following, a review of the determinations of the Boltzmann constant k important for the new definition of the kelvin and performed in the last decade is given.


fundamental constant, Boltzmann constant, International System of Units (SI), revised SI, primary thermometry, Johnson noise


Benz, S. , Fischer, J. , Fellmuth, B. , Gaiser, C. , Pitre, L. , Sparasci, F. , Risegari, L. , Gavioso, R. , Rippa, D. , Hallstedt, B. , Qu, J. , Feng, X. , Zhang, J. , White, D. , Gianfrani, L. , Castrillo, A. , Moretti, L. , Darquie, B. , Daussy, C. , Briaudeau, S. , Kozlova, O. , Segovia, J. , Martin, M. , del, D. and Moldover, M. (2018), The Boltzmann Project, Metrologia, [online], (Accessed May 29, 2024)


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Created February 5, 2018, Updated November 10, 2018