A simple calculator to calculate radioactive decay for a variety of radionuclides. Activities may be entered in Bq or Ci and conversions between these units is possible within the app. Many common radionuclides, especially those used in Nuclear Medicine and Positron Emission Tomography (PET), are predefined in the app. Users may add and save additional radionuclides and define the half-life. The decay calculator allows the user to enter a radionuclide, reference date and reference time. The c