Provided are a pixel array and an image sensor. The pixel array includes a plurality of pixels, which are arranged in a matrix form and which convert an optical signal into an electrical signal. The pixel array includes a first pixel arranged in a first row of the pixel array and a second pixel arranged in a second row of the pixel array, wherein each of the first pixel and the second pixel includes a first memory storing a digital reset value according to internal noise, the first memory of the first pixel stores m-bit data (where m is a natural number equal to or greater than 2), and the first memory of the second pixel stores n-bit data (where n is a natural number less than m).