A petabyte is 1015 or 1,000,000,000,000,000 bytes.
One petabyte (abbreviated "PB") is equal to 1,000 terabytes and precedes the exabyte unit of measurement. A petabyte is slightly less in size than a pebibyte, which contains 1,125,899,906,842,624 (250) bytes.
Since most storage devices can hold a maximum of a few terabytes, petabytes are rarely used to measure the storage capacity of a single device. Instead, petabytes are more commonly used to measure the total data stored in large computer networks or server farms. For example, Internet companies like Google and Facebook store over 100 petabytes of data on their servers.
NOTE: You can view a list of all the units of measurement used for measuring data storage.