Convert gigabytes to megabytes

One gigabyte is 1000 megabytes. To convert any amount, multiply by 1000. Going the other way, one megabyte is 0.001 gigabytes.

Multiply the gigabyte figure by 1000. So MB = GB × 1000. For a quick mental estimate, multiplying by about 1000 gets you within a percent or so, which is close enough for most everyday purposes.

One gigabyte is about two hours of HD video. A gigabyte is one billion bytes. A drive sold as 1 TB holds 1,000 GB decimal, which your operating system may display as 931 GiB — nothing is missing, the units differ.

One megabyte is a high-quality photo. A megabyte is one million bytes. Mobile data allowances, file sizes and download figures almost always use this decimal definition.

Because two different definitions are in play. Storage manufacturers use decimal units — 1 TB means exactly one trillion bytes. Windows and many other systems display binary units but label them with decimal names, so they show that same drive as 931 "GB" when they mean 931 gibibytes. Nothing is missing and nothing is faulty; the drive holds exactly what it says, measured differently. The IEC standardised kibi, mebi and gibi in 1998 specifically to end this, but adoption has been patchy.

Yes — both decimal and binary prefixes are exactly defined powers, so every figure here is exact rather than approximate. The results are shown to seven significant figures; the underlying arithmetic uses full double precision.