Reply To: The Random Gaming Freepost Thread

It turns out that the answer has to do with your electronic devices and their operating systems using a different definition of “gigabyte” (“GB”) than that of the manufacturer’s of storage devices such as memory cards and hard drives. When manufacturers of such devices say “GB”, they mean what is called a “decimal gigabyte”, which equals exactly 1,000,000,000 (one billion) bytes (a byte is a fairly basic unit of storage in computers). When your device’s operating system describes the capacity of the storage medium, they typically use what is called a “binary gigabyte”, which equals exactly 1,073,741,824 bytes. Because of this discrepancy, a device has less binary gigabytes than decimal gigabytes.

It turns out that a decimal gigabyte is approximately 93% the size of a binary gigabyte, so if your hard drive is 40 decimal gigabytes, your operating system will report that it is approximately:

40 decimal gigabytes * 93% = 40 * 0.93 = 37.2 binary gigabytes

Which is exactly the hard disk capacity that is reported by operating systems such as Windows XP. Likewise, a 1 decimal terabyte hard drive is 1000 decimal gigabytes. Windows will report that hard disk’s capacity as approximately:

1000 decimal gigabytes * 93% = 1000 * 0.93 = 930 binary gigabytes (this is very close to what Windows reports; however, the multiplication factor isn’t exactly 0.93, as we’ll see below)

So simply put, when you purchase a digital storage medium, you can expect your operating system to identify it as being about 93% the size that you expect it to be. You’re not being ripped off; it’s just that the word “gigabyte” is used to mean two different things.