There are 1,024 MB (megabytes) in 1 GB (gigabyte).
This follows the binary system used in computing, where:
1 GB = 1024 MB
1 MB = 1024 KB
In some cases (like storage manufacturers), they use the decimal system:
1 GB = 1,000 MB
However, the standard for most computing contexts is 1,024 MB per GB.