Radioactive Decay Calculator for Isotopes Commonly Used in Biomedical Research

Calculates amount of radioactivity remaining in a sample of isotope or isotopically labeled compound after a given period of time has elapsed.
(1) Choose your isotope from the radio buttons on the left of the screen.
(2) From the Reference Date drop-down menu, select a date corresponding to the reference date ("day 0" of radioactive decay, indicated in the manufacturer's documentation).
(3) The current date should be automatically displayed in the Today's Date drop-down menu; if you wish to know the radioactivity remaining on a date other than the current date, select that from the Today's Date drop-down menu.
(4) In the Radioactivity on Reference Date box, enter the initial total radioactivity in the sample (usually indicated in the manufacturer's documentation). Select the corresponding unit of radioactivity from the drop-down menu to the right.
(5) Click the Calculate button and the result will be displayed in the Radioactivity Now box.