Q&A: Why is my 300GB drive only 270GB?

[Red Squirrel]

Ever wonder why drives are always smaller then advertised? Here's why. 1KB = 1024 bytes, 1MB = 1024 KB, and so on.

So 1GB is equal to 1073741824 bytes. (1024^3)

But manufactureres use the words Killo, Mega, Giga in general terms instead of computing terms, as normally a Kilo is 1000, and so on. So your 300GB drive is actualy 300GB in "regular" measurements (1 killowatt = 1000 watts, for example).

So lets do the math and find out how much REAL GB a manufacturer measured 300GB is.

Take 300,000,000,000 bytes (what the drive actually is) and divide it by 1024 3 times.

What do you get? 279.34GB

A "real" 300GB drive should really be 322,122,547,200 bytes.

So because of the way manufacturers say that 1,000,000,000 bytes is 1GB, we buy drives much smaller then advertized.

They've been doing this for years. With 10Gig drives you dont really notice, but when you get in the 100's you do notice!

Even a 320GB drive is actually 298GB.


Partitioning also takes up a small amount of space but contrary to what some may say, the fact that the drive apears much smaller is not only because of the partitioning.

Archived topic from Iceteks, old topic ID:4464, old post ID:35824

[Chris Vogel]

We have binary prefixes to address this problem, but they aren’t used much unfortunately. The SI prefixes have strongly standardised meanings, and it was wrong to deviate from them.

Richardj posted information on a class-action suit against Western Digital for this very thing.

Archived topic from Iceteks, old topic ID:4464, old post ID:35826

[Triple6_wild]

ok lets see if i got this right

my 250gb drive is really 232.83???

231.89 is shown as avalible space

so partitioning or whatever took a lil less then a gig? right?

or is there other stuff also cutting avalable space down?

Archived topic from Iceteks, old topic ID:4464, old post ID:35830

[Red Squirrel]

Yeah that seems about right I would think.

Archived topic from Iceteks, old topic ID:4464, old post ID:35831