Provided herein may be a memory system and a method of operating the same. The memory system may include a memory device including memory cells, each having any one of an erased state or one of a plurality of programmed states, and a memory controller configured to estimate an optimal read voltage associated with at least one of the erased state or one of the programmed states based on a threshold voltage distribution corresponding to at least one of the programmed states. The memory controller may include a threshold voltage distribution checker configured to check a first threshold voltage distribution corresponding to a first programmed state, among the programmed states, and determine an average threshold voltage of the first threshold voltage distribution, and an optimal read voltage estimator configured to estimate a second optimal read voltage corresponding to a second side of the first threshold voltage distribution.