The kilobyte is a multiple of the unit byte for digital information. The International System of Units (SI) defines the prefix kilo as 1000 (103); per this definition, one kilobyte is 1000 bytes. The internationally recommended unit symbol for the kilobyte is kB.
However, in information technology, particularly in reference to digital memory capacity, kilobyte instead denotes 1024 (210) bytes. This arises from the powers-of-two sizing common to memory circuit design. In this context, the symbols K and KB are often used.
In other words, But there are really 1024 bytes in a kilobyte. Again, the reason for this is because computers are based on the binary system and 1024 is equal to 210 bytes.