Actual size on hard drive

[ljCharlie]

Can anyone explain why after a hard drive, let's say 20GB, is formatted, the hard drive capacity is only 18.6GB or something along that line? The capacity tends to decrease more as the hard drive size gets larger. For example, I installed a 120GB Westerndigital harddrive with 8MB of cache and I lost 8.3GB of space after formatted. Am I doing something wrong or is the manufacture actually telling consumer the wrong number? For instance, on a Westerndigital wesbite a 20GB WD200BB hard drive, the specs show a formatted capacity of 200,049 MB but after I formatted the hard drive, the realized or actual size is approximately 1,449MB less the total size than what's reported on the Westerndigital webpage.

Any response is appreciated.

ljCharlie

[RJ]

That is because the manufacturers use the wrong factor of "1000" to calculate the sizes. The correct factor is 1024 (1 KB = 1024 Bytes and so on)

So to calculate the real space take the GB number shown on your hard drive multiply it 3 times by 1000 to get Bytes.
So a "200 GB" hard drive would have 200.000.000.000 Bytes.
Divide that 3 times by 1024 to get the real GB.

200.000.000.000 Bytes / 1024 = 195.312.500 KB
195.312.500 KB / 1024 = 190.734,86328125 MB
190.734,86328125 MB / 1024 = 186,2645 GB

So a 200 GB hard drive has a real capacity of 186 GB (and a 20 GB hard drive has 18,6 GB).

It's all about marketing. Same happens to DVD. A DVD-5 holds 4,37 GB and a DVD-9 7,95 GB.

RJ