How many megabytes are there in a gigabyte?

1,024.

According to the American Heritage Science Dictionary, one gigabyte is a unit of computer data storage or memory capacity equal to 1,024 megabytes. The prefix giga means one billion or 10⁹,  therefore a gigabyte means roughly one billion bytes, or to be accurate 1,073,741,824 or 2³⁰ bytes.