This package consists of several macros that are shorthand for a variety of physical constants, e.g. the speed of light. The constants can be used in two forms, the most accurate available values, or versions that are rounded to 3 significant digits for use in typical classroom settings, homework assignments, etc. Most constants are taken from CODATA 2018, with the exception of the astronomical objects, whose values are taken from International Astronomical Union specified values. Constants that are derived from true constants, e.g. the fine structure constant, have been calculated using the accepted values of the fundamental constants.