Systems and methods for controlling desalting and dehydration of crude oil, one method including monitoring total dissolved solids (TDS) content at an outlet stream from a crude oil separation unit, the outlet stream comprising water; monitoring basic sediment and water (BS&W) content at an outlet stream from the crude oil separation unit, the outlet stream comprising processed crude oil; determining pounds per thousand barrels (PTB) salt content and volumetric water content of a dried, desalted crude oil product stream using the TDS content and BS&W content; and controlling a process input to the method from a comparison between the PTB salt content and volumetric water content of the dried, desalted crude oil product stream versus a maximum set value for PTB salt content and volumetric water content of the dried, desalted crude oil product stream.