Information at the foundation of modern science and technology from the Physical Measurement Laboratory of NIST.

	NOTE! On the public site this page redirects to: https://www.nist.gov/pml/fundamental-physical-constants
	Detailed contents
	Values of the constants and related information Searchable bibliography on the constants
	In-depth information on the SI, the modern metric system
	Guidelines for the expression of uncertainty in measurement
	NIST Uncertainty Machine
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	Online: February 1998  -   Last update: December 12, 2017 Privacy Policy / Security Notice   -   NIST Disclaimer