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Monday, August 4

Why Is My Hard Disk (HDD) Smaller than the Size It Says ? Here's Why !

You may purchase a Hard Disk Drive (HDD) but upon getting home & plugging it in the desktop/laptop, you wonder why the actual size is smaller than the size the manufacturer advertised ?

This is because of mathematics. Yeah, mathematics.

Hard disk manufacturers consider :

1 Kilobyte = 1000 Bytes,
1 Megabyte = 1000 Kilobytes
1 Gigabyte = 1000 Megabytes.

This is, however, not true. The real values are :

1 Kilobyte = 1024 Bytes,
1 Megabyte = 1024 Kilobytes (1048576 Bytes)
1 Gigabyte = 1024 Megabytes.

You bought a 20Gb hard disk, the actual size of the hard disk is only 19Gb and a 80Gb hard disk is actually 74.5Gb

20 Gb - 18.62 actual Gb
40 Gb - 37.25 actual Gb
60 Gb - 55.87 actual Gb
80 Gb - 74.5 actual Gb
100 Gb - 93.13 actual Gb
120 Gb - 111.75 actual Gb
160 Gb - 149.01 actual Gb

These are the actual numbers:

1MB = 1024 bytes
1GB = 1024 MB
So a true GB = 1024 x 1024 = 1,048,576 bytes

But when manufacturer's rate the drives, they use 1000:

1MB = 1000 bytes
1GB = 1000 MB
So their GB = 1000 x 1000 = 1,000,000 bytes

Here's how to figure the true capacity of your HDD. You have an 80GB drive, so in manufacturer's terms, that means:

80 x 1,000,000 = 80,000,000 bytes

But if you divide it by 1,048,576
you'll get the 'true' capacity ..

80,000,000 / 1,048,576 = 76.29 GB .


rogard said...

Hi there, chocolata :-)

I just stumbled over your blog while browsing subscene's inner sanctum.

Impressive English, nice writing style and both funny and informative.
The only thing you obviously need to work on is your taste in films. ;-)
Well, hold on, not exactly your taste because that seems to be okay - but why on earth do you even watch so many of those crappy films like "bottoms up"? Yukk... So it's more a problem with your decision-making which one to watch and which to skip I guess. :P

Anyway, CU around on subscene



PS: The size of the actual hard disk capacity is further reduced by the file system (reserved blocks with data about the files and folders etc.) Effectively, you lose a couple of MB but with large drives nowadays nobody really notices any more. It's around 0.1% of the total unformatted capacity.

Back in the olden days of 8- and 16bit computing it used to make quite a difference between unformatted and formatted media capacity (ca. 10-15%). But I am digressing...

Anonymous said...

Thank you teacher...