HDD Lost Space

[Softstag]

Hi

Does anyone know how to calculate how much hard drive space will be used by the file system (FAT32 or NTFS) when a hard drive is formatted? Do you know of a tool that can calculate this?

I often get asked why there is only 74Gb space on a blank 80Gb HDD. I know that part of this is down to the way HDD manufacturers quote GBs, the rest is down to the space required to put the file system on the HDD. I want to know how to calculate how much free space you will get after formatting a drive.

 

[hergieburbur]

HD Manufacturers quote HD space using a GB a 1 Billion bytes, whereas, in actuality, a GB is closer to 1.073 Billion bytes. That is where a lot of the difference comes from. As a (very) rough estimate, you can multiply out the size according to the manu. specs, and divide by 1.073 billion. I.E.

80 Manufacturers GB = 80000000000
1 actual GB ~ 2^30 or about 1073000000
So
80000000000/1073000000 = 74.55 GB, which is close to what you are seeing.

That is the main factor, though I think that which cluster size you use will have a very small influence on the outcomeas well (Close to infintesimal).