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Fundamental Constants Data Center

The Fundamental Constants Data Center is focused on physics relevant to the determination of values of the fundamental constants of physics and chemistry.

Activities include gathering and analyzing information for, and carrying out periodic least-squares evaluations of the constants. When necessary, new theoretical calculations are carried out to provide additional information for the adjustments. The Data Center is also involved in the development of the International System of Units, which is the basis for expressing the values of the constants. Support for research relevant to the fundamental constants and tests of basic laws of physics is provided through the Precision Measurements Grants Program.

News and Updates

Projects and Programs

International System of Units (SI)

The International System of Units (SI) provides definitions of units of measurement that are widely accepted in science and technology and which set measurement

Precision Measurement Grants Program

Since 1970, the National Institute of Standards and Technology (NIST) has awarded Precision Measurement Grants for significant research in the field of


An introduction to the new SI

Peter J. Mohr, Sandra Knotts, William D. Phillips
Plans are underway to redefine the International System of Units (SI) around 2018. The new SI specifies the values of certain physical constants to define units


Group Leader