A gigabyte is much larger than a megabyte. According to the National Institute of Standards and Technology, there are 1000 megabytes in a gigabyte. However, in some cases, a gigabyte is defined as 1024 megabytes.
Usually, a gigabyte is defined as 1000 megabytes in computer storage, such as when referring to the capacity of a hard drive. For processor storage or virtual storage, however, a gigabyte is commonly defined as 1024 megabytes. This is equivalent to a 2 percent difference, so the two definitions are approximately equivalent. It takes about 3 megabytes to hold a single song and 1 megabyte to hold a picture of moderate quality. Meanwhile, high-definition movies take up about 1 gigabyte of space.