One gigabyte (GB) equals 1,024 megabytes (MB) in binary storage terms, which is the standard used by operating systems and storage devices. In decimal terms, 1 GB = 1,000 MB, sometimes called a gigabyte in marketing contexts. The binary definition (1,024 MB) is more common in computing because storage systems use powers of 2. This is why a hard drive advertised as 1 TB often shows as slightly less when you check your computer—manufacturers typically use the decimal definition (1,000 GB per TB), while your operating system displays it using the binary definition (1,024 GB per TB). To convert any number of gigabytes to megabytes, multiply by 1,024 (or 1,000 if using decimal).