There are 1,024 MB in 1 GB. MB stands for megabyte, and GB stands for gigabyte. Some manufacturers of storage devices, such as flash drives, measure 1 GB as an even 1,000 MB.
Computers use a base-2 system, which is why they measure a gigabyte as 1,024 megabytes instead of 1,000. One bit is the minimum amount of data, representing one signal of "on" or "off." One byte is the same as 8 bits, and one letter in a text document is 1 byte of data. One kilobyte of data is 1,024 bytes, 1 megabyte of data is 1,024 kilobytes and 1 gigabyte is 1,024 megabytes. The system goes on to terabyte, petabyte, exabyte, zettabyte and yottabyte, with each unit being 1,024 of the previous unit.