A controller for controlling a memory device including memory cells, the controller includes: a memory suitable for storing offset level information which is determined based on a sample read level according to characteristics of the memory cells and Gaussian modeling of the memory cells; and a processor suitable for generating an estimated read level based on the Gaussian madding and data read from the memory cells, and applying a compensated read voltage to control the memory device to perform read operations of the memory cells, wherein the compensated read voltage is generated by applying the offset level information to the estimated read level.