The petabyte is a multiple of the unit byte for digital information. The prefix peta indicates the fifth power of 1000 and means 10 15 in the International System of Units (SI), and therefore 1 petabyte is one quadrillion (short scale) bytes, or 1 billiard (long scale) bytes. The unit symbol for the petabyte is PB. 1 PB = 1000000000000000B = 1015bytes = 1000terabytes.