How many GB are there in one TB?

1,024.

There are 1,024 gigabytes in one terabyte of electronic data. This is according to the definition of a terabyte from the American Heritage Science Dictionary. The prefix tera means one trillion or 10¹²,  therefore a terabyte means roughly one trillion bytes, or to be accurate 1,099,511,627,776 or 2⁴⁰ bytes.