Drive size discrepancy on new PC

  davehyde 12:20 18 Jan 2003
  davehyde 12:20 18 Jan 2003

My new PC was bought as advertised with an 80Gb hard drive.

Looking at drive properties, now I've started to copy files over from the old PC, just to see how much space I've got left (to feel smug, as my old one only had 7Gb)

I was surprised to see that the drive size is reporting as 74.5GB..

Is there any logical reason for this?


  1st RHA 12:29 18 Jan 2003

This is usually installed with recovery partitions and all sorts of safety devices which is quite bulky, seems about right to me.

  Diemmess 12:31 18 Jan 2003

Yes its the mathematicians being devious!

I Kb = 1024bytes and so on ....By the time you talk in Megabytes or Gigabytes you have different figures depending on whether you are being modest or trying to sell the thing.
You have not been sold short, and have a wealth of lov-erly memory.

  flecc 12:34 18 Jan 2003

Yes, Hard Drive manufacturers measure size arithmetically as 1000 bytes to the kilobyte, but in our computers the kilobyte we use is actually 1024 bytes, a megabyte is actually 1024 kilobytes, and a gigabyte is actually 1024 megabytes.

Therefore the Gigabyte you see after formatting is actually 1024 x 1024 x 1024 which equals 1,073,741,800 bytes or roughly 1.074 gigabytes.

If you divide your manufacturer's arithmetical gigabytes by 1.074, you will have the computer gigabytes that you see in Windows. For example, 30 gigabytes will become roughly 27.9 gigabytes in Windows.

In addition, some space is wasted by the file sytem in use and the partitions used, and this varies with the different file systems (Fat16, FAT32, NTFS), the size of the partitions, and the influence of third party software like Partition Magic for example.

With hard drives getting bigger all the time, think what fun we'll have working out Terrabytes and Petabytes! Yes that's right, the 1 million gigabyte hard drive is already being planned for!

This isn't dishonesty on the part of hard drive manufacturers, The eventual size is determined by the formatting method and file system used, and the manufacturer has no control over this so reports the simple arithmetical gross size.

  davehyde 15:14 18 Jan 2003

I knew there'd be some logical answer!!


(ps I'm still 67Gb up on my old PC!!)


  Djohn 15:19 18 Jan 2003

davehyde, you will never fill it all up! three years ago we would say that about 2.5 gig drives. :o)

  BlueMeanie 15:21 18 Jan 2003

80 Gb ÷ 1.024 ÷1.024 ÷ 1.024 = 74.506


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