In this case, 1GB equals 1,024MB, so 1GB is twice as much as 512MB.

Here is the progression, starting with the smallest:
* Byte: base unit
* Kilobyte (KB)
* Megabyte (MB)
* Gigabyte (GB)
* Terabyte (TB)
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Now, here's where it can get confusing...there are actually 2 different definitions in use, something that most people aren't aware of.

Technically, 1 kilobyte (KB) equals 1,000 bytes, 1 megabyte (MB) equals 1,000 kilobytes (KB), etc. That's is the official standard, and what hard drive manufacturers use. (A 1GB hard drive equals exactly 1,000,000,000 bytes.)

However, when it comes to RAM manufacturers and most software (including Windows), a different definition is used...they say that 1 kilobyte (KB) equals 1,024 bytes, 1 megabyte (MB) equals 1,024 kilobytes (KB), etc. This is not entirely correct according to some of the leading institutions and organizations in the tech community! They are correctly measuring the amount of memory or space, but telling you they've measured it in a unit other than what they really did. They really measured it in ''kibibytes'' (KiB), ''mebibytes'' (MiB), etc. But because few have even heard of these measurements they simply say ''megabyte,'' ''kilobyte,'' etc for familiarity sake. (Note: This is from the 'new' perspective. Some still use the older definition, which said that 1MB was indeed 1,024 kilobytes. Thus, you could debate whether or not the measurement is technically correct or not.)

This is why if you purchase a 100GB hard drive, Windows will tell you the total space is 97GB or so. The hard drive manufacturer didn't screw you, they just used a definition of measurement.

Hope this helps,
John