Moisture determination in fertilizers by the application of Archimedes Principle drive the author to the following equation were u = moisture in percentage d = fertilizer density x1= difference between the sample dry weight and the buoyed up by a force equal to the weight of the displaced fluid (saturated solution of the fertilizer) y= sample weight d1= density of the fluid. For seeds the following equation was obtained were u = moisture in percentage v - seeds volume d = seeds density y'= seeds weight The application of both formulas showed straight correlation with the usually method in store at 100-105°C.