A kilobyte, abbreviated K or KB, equals 1,024 bytes, but is commonly rounded to 1,000. A megabyte, which is abbreviated M or MB, equals one million bytes (actually 1,048,576 bytes). Gigabyte, abbreviated G or GB, represents about 1 billion bytes (actually 1,073,741,824 bytes). Terabyte, abbreviated T or TB, equals about 1 trillion bytes (actually 1,009,511,627,776 bytes). A petabyte equals about 1 million gigabytes.