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I just got a new Lenovo Laptop which has been installed with Windows 7 and is supposed to have 250 GB hard disk.

Windows 7 reports that the hard disk drive has two parts: 221 GB C: and 9.76 GB Lenovo Recovery. The sum of the two parts is 230.76 GB.

If I remember correctly, if divide 250 GB by 1024 three times, I will get 232.8 GB, which should be what the OS reports as the hard drive size. But why the sum 230.76 GB of the two parts of hard drive is still smaller than 232.8 GB?

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For anyone that lands here, please read the question more carefully than the people who posted answers below. First of all, Tim had already accounted for binary/decimal units, so it’s not a matter of 1,000 vs. 1,024. Second, he was not asking about the free space on the drive being too low, he was asking about the total space, so it has nothing to do with file-system overhead. –  Synetech Nov 24 '13 at 21:31

5 Answers 5

up vote 12 down vote accepted

Because NTFS by design uses a piece of your volume for a MFT (Master File Table) which holds file names, creation dates, access permissions, and contents as metadata. The bigger the volume, the bigger the chunk NTFS will need.

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Do you also mean the whole C: disk size does not include the size for MFT? Is there some place under Windows reporting the size of the whole hard drive? –  Tim Nov 18 '09 at 4:58
    
Yes, The size reported is not including the MFT. I don't think anything within Windows will report the full actual size of the disk including the part the MFT is taking up. –  John T Nov 18 '09 at 5:19
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No, the size does include the MFT. Think about it the MFT can grow so it the size didn't include the MFT you would see the size of the drive drop. Also in Disk Management if you switch the format from NTFS to FAT the size of the partition doesn't change. –  shf301 Nov 18 '09 at 6:18
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@shf you are very misinformed, and very downvote happy. First of all, the MFT size is defined by the size of your drive, and it is made once. This space allocated does not change in size, it preallocates enough up front for future changes. Also once you changed to FAT32, try a reboot? –  John T Nov 18 '09 at 6:50
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Maybe you are thinking of the MFT zone which NTFS reserves, but that is not the size of the MFT itself and that zone can be used to store files if the rest of the drive is filled. See technet.microsoft.com/en-us/library/cc781134%28WS.10%29.aspx –  shf301 Nov 19 '09 at 5:20

Actually. This is because harddrive manufacturers conform to the 1MB = 1,000 KB rule and your OS uses the 1MB = 1,024 KB rule.

This would probably account for most of your lost space. Its normal. You will NEVER buy a drive that is the size it specifies, ever. I looked in to it myself not too long ago :)

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Ah, you mentioned something like that also. Ah well, good clarification for everyone else! :D Also, NTFS holds additional space/information for each additional partition used, so you will probably never see 100% of your space within Windows. –  SevenT2 Nov 18 '09 at 5:33
    
All the drives you buy are the size they specify. Your software is just reporting the size wrong. –  endolith Jun 15 '11 at 4:59
    
Re-read the question (even the original); he already accounted for that. –  Synetech Nov 24 '13 at 21:25

Unfortunately, life's a bitch and this is one of those things that annoys people non stop.

At least you are smart and understand that there is a conversion that needs to be made.

The "extra" space is usually used up by the allocation table, meta data and various other items that just make it work without you needing to think of it... it is nothing to worry about.

If you want to make 100% sure you have the correct drive, go in to device manager and expand hard drives, find the model number and Google it. If it reports the correct drive (which it should) there shouldn't be anything to worry about.

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He’s not asking about free space, he’s talking about total space. The total size of the volume is not affected by file-system structures, only the free space would be. The total volume size includes the MFT and other NTFS special files. –  Synetech Nov 24 '13 at 21:28

A chunk of your loss at least is due to the partition table eating it's entire track--a horribly inefficient legacy we are left with.

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Um, what‽ Partitions tables are only a few clusters; there’s no way partition tables would take up 2GB! –  Synetech Nov 24 '13 at 21:26
    
Except they eat one track as the next partition needs to start on the next track. I do agree it's not 2gb, though. –  Loren Pechtel Nov 24 '13 at 23:28
    
Yes, that was one of the things that always annoyed me whenever I tried to size my partitions accurately; the partition programs would always round. But no, it’s indeed not 2GB, it’s ~7MB, plus, the excess doesn’t just disappear, it gets added to the previous/next partition. –  Synetech Nov 24 '13 at 23:41
    
@Synetech It depends on the capacity of a track. I really doubt a 4tb drive has 7mb tracks. –  Loren Pechtel Nov 24 '13 at 23:52
    
I don’t think that’s how it works; it doesn’t use up a whole track. You can check with a partition program; just use the resize function and observe how it rounds the partition size on different sized drives. Over the years, I have seen these programs round to the nearest ~7.5MB on drives of all sizes. –  Synetech Nov 25 '13 at 0:01

It could just be the manufacturer rounding the hard drive size to the nearest whole gigabyte. If we start with what Windows shows and calculate what that work out to in billion bytes:

232.8 * 2^30 / 10^9 = 249.9671 million bytes

So they just rounded the marketing size to 250, cause whose going to miss 0.0329 million bytes.

If you can get the module number of the hard drive and get it's detailed specs and find it's sector count you can determine what the actual capacity of the drive really is.

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