For those needing portability, Rad Pro for Desktop works with Windows 8.1/10 tablets. Will not work with Surface tablets running Windows RT.
                =Select Activity UnitsCalculated GramsSelect Isotope

Select Calculation Direction
Uranium and Plutonium Grams Calculator
Select Isotope Group
Select Number of Isotopes
Enter pCi
Plutonium SA Uranium SA
UK Radiation Adviser Nuclear Links Nuclear Jobs MARSSIM Nuclear Resources US Health Physics Society Author's Personal Website US Health Physics Consultant UK Radiation Protection Society NRRPT Study Kit and Classic RP College Textbook

Rad Pro Calculator Recommends These Links

Utilizing the specific activities of the uranium and plutonium isotopes, calculate the grams of PU and U from known activities or calculate the activities from know masses.  If you select multiple isotopes, the total uranium and total plutonium are also calculated for you.