Where does the hard drive size go?

Something which has always been a problem for many people is disk space. No matter how much you have, you somehow mysteriously use up all of it. It makes me wonder why hard drives never have the claimed capacity.

It was a long while since I bought a PC, or reflected over their disk size, but I’m sure this goes for Dell, HP and all the others as well. In the case of Macs, let me express how dissatisfied I’ve been with the hard drives who have come with my two MacBook Pros. Last year, I got my first Mac, and it was supposed to have a 100GB hard drive. Actual size: 92 GB.

Now, at my new job I got a MacBook Pro which were to sport a 160 GB hard drive.
Actual size: 148 GB. That is about a 8% hard drive size loss for each machines. Size that has been payed for.

I’m not sure if I miss anything, if the system or whatever needs that size, and I can live with some of it being claimed by anything making it work. But the actual size should still be what’s promised in the specifications, right?

Give me back my gigabytes!


  • Gerben says:

    Hard drive manufacturers measure using the decimal (not binary) system. So 1KB is 1000Bytes, while computers say 1KB is 1024Bytes. This way the size you see in your OS doesn't match what the manufacturers say.

    So in the case of your 160 GB drive. 160 * 1000^3 = 160000000000Bytes.

    160000000000 / 1024^3 = 149GB

  • Jaap says:

    What Gerben said… I was under the impression that everybody knew that… quite a fitting domain name there Gerben. (algemeen bekend translates to generally known).

  • HÃ&Acir says:

    AFAIK those missing parts are used for holding data about partition tables and some other stuff like that.

    This is same as iPod's. For example iPod nano 4GB is actually 3.7GB. You are damn right about advertising, they should advertise what they are giving us.

  • Sigurdhsson says:

    As said by Gerben it's because computers use 1024 where the manufacturers use 10^3 – that's why the new prefixes Ki, Gi, Ti, etc are emerging. That way 160GB is always 160GB, but in computers you'd list it as 149GiB.

    And I think apple has a disclaimer about this (bottom of the apple.com shop page), in small, grey text, as if they didn't want yo to see it ;).

  • Carl says:

    The hard drive space is actually being by depleted by gamma rays during the transcontinental flight to Sweden. These rays would normally be deflected by the ozone layer in the Earth's atmosphere. Blame global warming. πŸ™‚

  • Scott Powers says:

    Ya learn something new every day. Didn't know they used different measurement systems either. I've wondered about those missing GB's myself many time.

  • Disk allocation and differing byte counting aside, OmniDiskSweeper is a great tool to keep track of were the rest of that space went (that which you do have at your disposal ;)) and if you pay the license fee, you can delete stuff directly from the application as well.

  • AndrÃ&A says:

    Unfortunately this goes back to the early days of desktop computers. Specially when hard drives started coming out with over 1Gigabyte of storate… I'm sure some marketing smart-ass decided to scam their customers with the 1024 bytes = 1kilobyte story. Then, next thing we know, every single manufacturer is adopting the same marketing strategy! Now, it's common place.

    This different comes from the binary system. Computers store bits. If you want to know how many elements you can name with any given number of bits you just power two to the number of bits and you get their span:

    2^1 = 2 => you can name two addresses with 1 bit (0,1)

    2^2 = 4 => you can name 4 addresses (00,01,10,11)

    2^3 = 8 => 8 addresses (000,001,010,100,101,110,011,111)

    2^10 = 1024, so people didn't want to simply ignore those extra 24 places just to make it easier for common folk to read "kilobytes".

    Thus was born the different of the prefixes Kilo- Giga- Tera- Peta- when it comes to bytes.

    ( Thought someone might want to know the story behind the 1024… πŸ˜‰ )

  • OJ says:

    GB is now a very common synonym for the base-10 system, and hence the manufacturer is actually correct.

    The term you're looking for is Gibibyte which is where the powers of 1024 come into play.

    Just FYI πŸ™‚


  • Robert Nyman says:

    Wow, thanks! Maybe I should've thought of the 1024 situation, but it completely passed my mind. Besides, I think a lot of people do expect that when they buy a computer, so, while completely correct, I think the resellers are a little bit tricky.

    I mean, people will look at how large their computer syas the disk is, compare to the ad, and be dissatisfied.


    You cheeky, you… πŸ™‚

    Actually, I think the ozone layer is in fairly good shape over Sweden, thank you very much. πŸ™‚

  • Jeff L says:

    Google is stealing my hard drive space.

    I've been wondering where it has been going, and I found the culprit…Google Desktop.

    The index file is something around 5GB for my machine, and constantly growing I assume.


  • Robert Nyman says:


    Wow, that's a pretty large index file!

  • Nikke says:

    Perhaps they're trying to get away without starting new datacenters and are harnessing home computers instead. Just like Seti@Home πŸ˜‰

  • Nikke says:

    Uh… And by they I mean Google ofcourse.

  • Robert Nyman says:


    Ha ha!, Yeah, maybe! πŸ™‚

  • I am not sure if the 1024 story is the reason. After all, if it says 80Gb no matter if this is or not bytes, 80Gb can't just be 72Gb when you look at it.

    AFAIK, the thing is that a 80GB HD has 80Gb of raw space. You can actually store 80*1024^3 bytes, but that is an obscene amount of data and you need to organize it some way. That is when the Filesystem comes in and takes a part of it for the Allocation Table.

    The more complex your filesystem is, in general, the more space it takes. Using a fairly complex FS with journaling, user permissions and three levels of users (like Unix systems like Mac do) takes more space than using the old FAT 32 system.

    Moreover, there is the block size. Data is stored in small indivisible sequencial blocks and its size may vary.

    Because they are indivisible and sequencial, part of them is wasted for every file, so you have an average waste of (number of files)*(block size)/2. To prevent this you can reduce the block size, but keep in mind that this will affect performace and also may reflect on a bigger allocation table, because there are more blocks to index.

  • Dave says:

    I'd like to hear more about Google.

    My hard drive looses it's space to the tune of GB's within

    a 24 hour period.

    I even bought another 500 GB external hard drive last week.

    I cleared everything I could think of from my various folders

    and files.

    it freed up approx 7 GB"s.

    I unplugged the external hard drive and checked my drive space,

    approx 7 GB free space.

    The hard drive remains unplugged.

    I add no new programs.

    I use the computer very little, only checking e-mails.

    Two days later I get another low disk space warning.

    24 mega bites left.

    What in the world is up with all of this???

  • Alex says:

    Guilherme Zuhlke O’Connor

    The disc allocation information does use a bit of it, however, it does not use as much as you are saying. If you look at the spec sheet from the manufacturer of the drive, it will say that they are using the 1,000 system and not 1024. This is completely a marketing ploy that worked a lot better when people were using 1 to 5 gig drives, because then you could say the small amount left was being used by the access tables, however, with current 750 gig drives and terabyte drives, it just doesn't make sense and isn't true. If you call the company and complain enough, they will admit it, but not fix anything.

  • SyKo says:

    Alex is correct. This is just a bald-face lie and marketing ploy from drive companies and they've been stealing money from ppl for years w/ this tactic. It's only during recent years, since the major increase in drive size that we're waking up and seeing the truth about this. I currently have a 750gb hdd that is only actually 698.4gb in size. I would imagine the machine he was trying to get me to pay the extra 250 bux for with the 1tb drive would have only been around 930gb. When the avg person walks into one of these stores and sees, for example, "80GB Harddrive" on the box, guess how much drive space that person thinks their buying? 80gb of course. This holds true in the past for all the smaller drives as well, it's been this way for years, and the drive companies all what they were doing. It's false advertising and theft, plain and simple, isn't legal, and wouldn't be allowed to occur with any other product on this planet. Imagine buying cigarettes and only getting 17 in a box that said 20 on the top, or buying a dozen eggs to only find 10 in the carton once you got home. Then imagine how you'd feel calling the store to only have them tell you that it's just their own lil' "special math". -_-

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