Constants, Units & Uncertainty home page

Feedback We would like to hear from you! The Fundamental Constants Data Center seeks to facilitate your access to: Values of fundamental physical constants and energy conversion factors (with downloadable values) Searchable bibliography on the fundamental physical constants Information on the International System of Units (SI) Information on evaluating and expressing the uncertainty of measurement results We have compiled a list of frequently asked questions which may cover some of the questions you have. This site has undergone numerous improvements from comments from users like you, but we may not be able to respond personally to every inquiry. Please send us your ideas and recommendations using the comment form below. We appreciate your comments, which will be anonymous if an email address is not supplied. Comment form 1. What types of additional information would you like to have available? 2. Other comments: 3. Your email address (only if you want us to write you back): The information submitted on this form will be handled in a similar manner to E-mail, as described in the NIST: Privacy Statement / Security Notice   -   NIST Disclaimer