This is the question that many of us will have in their minds but hardly anyone knows the actual reason behind this. I too had the same question in my mind and after some real digging I know the reason now.
Why is the usable disk or memory space always less?
All the softwares calculate the space in a way different than the harddisk manufacturers. This is because any software calculate the space in powers of 2 only. So, for softwares 1KB = 2^10Bytes = 1024 Bytes.
On the other hand, manufacturers take 1000Bytes instead of 1024Bytes as 1KB, 1000KB instead of 1024KB as 1MB and so on.. May be they do this in order to make their calculations easy.
Now, let me give you a small example to make the concept more clear.
For a Manufacturer, 500GB hard disk is:
500 x 1000 x 1000 x 1000 = 500,000,000,000 Bytes
Now, for a software or a computer system 500,000,000,000 Bytes memory space is:
500,000,000,000/(1024*1024*1024) = 465.66 GB
This same thing applies to your pen-drives also.(Your 8GB pen-drive will actually be 7.45 - 7.50GB).
How much usable disk space do you get?
Based on the calculations shown above we can see that:
- For 8GB we are almost losing 0.5GB (We get 7.45GB , Do the calculations)
- For 250GB we are almost losing 20GB (We get 232.83GB , Do the calculations)
- For 500GB we are almost losing 35GB (calculations shown in the above example)
This shows that, more the space we buy, more we will be losing. Sad but true.
Now you know where the remaining memory space is going, right into the manufacturer's pockets.
I hope this will be helpful to you in understanding how the memory usage on different devces work. Let me know your thoughts in the comments below.