Recently bought a new Seagate external 1TB hard drive and saw it’s missing out gigs of space than what was promised. I have seen this before. But, on a small capacity hard drive, say 1 GB HDD, you won’t really mind missing out some megs of space. Years back when I checked with my instructor, he said it is some system files that’s occupying this space. But, even after formating the disk, it still didn’t show 1 GB total space. Though I felt the instructor was wrong, I didn’t want to question and prove him wrong and moreover, he only had that answer he told me. Later, I checked with another tech guy when I was doing my graduation and he said those spaces were used by hard disk clusters. This answer was more convincing because it made sense; maybe while manufacturing a 1 GB HDD, they use a bit of space for it’s own purpose. I believed that answer for few years, but when I bought 500 GB HDD, a lot of gigs were missing and it’s not the hardware that’s using and obviously not any system files. So, again my search began and was in vain. Finally, when I bought Seagate 1 TB HDD, I contacted Seagate to check why so many GB’s were missing out from my harddisk. I got the answer and it proved both the previous answers wrong:
The reason is because when they advertise 320gb hard drive they count 1mb of data is = to 1000kb when really it is 1024kb. Now that may seem like it wont matter but when you go up to the huge gigabytes it DOES matter. You can do this simple calculation test to find out yourself.
Go to my computer and right click your drive and properties. If you did partition and split the drive make sure you add both of them together. Anyways go to properties and take a look at the total space in bytes.
For example My E drive is my 1TB(1000gb) hard drive 1000097177600 bytes is what it says in properties
So according to the advertisement hard drive companies they call this a 1TB drive because they divide those bytes and round off 24kb off every Mb(so you lose out 24kb every 1mb and when that doesn’t seem much, that is going to seem a lot when you have huge hard drives like mine).
So put the number 1000097177600 in the calculator in bytes
copy and paste that number in the bytes and convert it, you will see its really 931GB of space. The exact same number I see in my computer and total space I can use for that drive.
Now you try with your drive, take a look at the bytes(if you split the drive into 2 partitions add both of them together and paste into the converter and you will get roughly 320,000,000,000 which again since the hard drive companies divide 1mb by 1000kb when its supposed to be 1mb for every 1024kb you lose all that extra space.
Every hard drive manufacture will state this rounding off in their fine print, take a look at this random western digital hard drive specs
Scroll to the bottom and you will see their fine print
As used for storage capacity, one megabyte (MB) = one million bytes, one gigabyte (GB) = one billion bytes, and one terabyte (TB) = one trillion bytes. Total accessible capacity varies depending on operating environment. As used for buffer or cache, one megabyte (MB) = 1,048,576 bytes. As used for transfer rate or interface, megabyte per second (MB/s) = one million bytes per second, megabit per second (Mb/s) = one million bits per second, and gigabit per second (Gb/s) = one billion bits per second.