How Can We Help?

Hard Disk Sizes (Reported vs Actual)

You are here:
< Back
Hard Disk Sizes (Reported vs Actual)
Last Updated: 06 Apr 2001

*** PLEASE NOTE: Link(s), If Provided, May Be Wrapped ***

From the dawn of time, Hard Disk manufacturers have used
the Decimal system (power of 10) to calculate disk space,
vs the much more accepted Binary system (power of 2) that
everyone else in the computer industry uses.

Every single storage vendor is using the following scale
to measure the capacity of their drives:

• 1 KB = 1000 Bytes
• 1 MB = 1000 KB
• 1 GB = 1000 MB
• 1 TB = 1000 GB
• 1 PB = 1000 TB

This means that when you purchases your 60GB EIDE disk,
you are actually getting less than that. And we haven't
even gotten to the part where the file system takes its
share of the usuable space.

Here's the handy-dandy chart to determine just how much
of a discrepancy there is between the vendors' numbers
and that of the actual numbers as reported by the BIOS
and Operating System. This info is in BYTES:

KB: (98%)                 1,000 vs                 1,024
MB: (95%)             1,000,000 vs             1,048,576
GB: (93%)         1,000,000,000 vs         1,073,741,824
TB: (91%)     1,000,000,000,000 vs     1,099,511,627,776
PB: (89%) 1,000,000,000,000,000 vs 1,125,899,906,842,624

Just multiple the number on the box by the appropriate
percentage (e.g. 60GB * 0.93 = 55.8GB) to find out what
your actual storage amount will be. The discrepancy will
only get worse as the disk density increases (e.g. you
will lose almost 93GB per TB), but now you have an easy
way to calculate just how much you're being "robbed" by
the Hard Disk manufacturers.




• This situation is not quite as bad as the situation
  with the Monitor vendors who were using arbitrary
  screen size measurements until up to a few years ago.
  The difference was that the amount of loss varied per
  vendor.  Take 17" monitors, for instance: while some
  vendors were giving you 16.1" viewable area, others
  were providing only 15.7" or 15.8". There was no
  consistency, and it led to lots of consumer confusion
  and angst. With the hard drives, at least, there is
  no difference between the vendors -- it's an Equal
  Opportunity mugging...

• This problem is not limited to Windows.  This is true
  for all modern desktop OSes.