Gigabytes to megabytes (GB to MB)

One gigabyte is exactly 1,000 megabytes. That is the definition of the prefixes, not a measurement: the decimal SI prefixes (kilo, mega, giga, tera) step by exactly 1,000, and the binary IEC prefixes (kibi, mebi, gibi, tebi) step by exactly 1,024. The two families are both exact; the trouble is only that software and storage labels do not always say which one they mean.

Worked through: 8 GB x 1,000 = 8,000 MB.

Going the other way, one megabyte is 0.001 gigabytes.

For mental arithmetic: Add three zeros.

Multiply by a thousand, and be ready for the answer to disagree with a file manager. The difference comes from the conversion the operating system is quietly doing: Windows reports a 1 GB file as 953 MB because it is dividing by 1,024 twice while printing the decimal prefix. macOS and Linux switched to decimal reporting years ago, which is why the same file can show two different sizes on two machines and both be telling the truth about different units.

Precision is worth matching to the input. A measurement given as 0.5 GB carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.