Confidence votes 4.8K. There are exactly 1 million gigabytes in a petabyte. 1 petabyte (PB) = 1,000,000 gigabyte (GB). There are similar units based on powers of two instead of powers of ten, but at these large sizes, they are very rarely used, if ever: 1 pebibyte (PiB) = 1,048,576 gibibytes (GiB).