A data compensating device includes a plurality of data compensating blocks. Each of the data compensating blocks includes: a memory cell configured to store an image signal; a one-time programmable (OTP) cell including a program transistor; and a calculator configured to output a compensation signal that is based on an offset signal output from the OTP cell and the image signal stored in the memory cell. The OTP cell is configured to output the output signal from the program transistor. The program transistor includes a gate oxide and is configured to be irreversibly changed based on the image signal. Thicknesses of the gate oxide of the program transistor of the OTP cell in different ones of the data compensating blocks are different from each other.