A memory system includes a memory device and a data converting device. The memory device includes a memory cell array which includes a plurality of memory cells. The data converting device includes an encoding device. The encoding device converts input data into converted data by changing a bandwidth corresponding to the input data, and provides the converted data to the memory device. Accordingly, the memory system is capable of improving the reliability of programmed data by changing the bandwidth corresponding to data to be programmed. A method of storing data in a memory system is also disclosed.