The prefix “giga” in the metric system refers to 10 to the 9th power, or 1,000,000,000 (one billion), so a gigabyte (abbreviated “GB“) is unit of measure referring to one billion bytes.

The term “gigabyte” is also sometimes used to refer to 1,000 megabytes, or 1,024 to the 3rd power, or 2 to the 30th power, in which case, a gigabyte would be 1,073,741,824 bytes. This definition is more common with RAM specifications, hard drive capacities, and file sizes. However, most standards bodies now discourage this usage, and instead recommend the IEC term “gibibyte” (GiB) for this usage.