External Hard Drive is full - why?

My 500 GB hard drive is nearly full, but  when I total the space used by the files, it’s no where near 500. And I just lost more space after sending some items to the recycling bin. Does anyone have a clue how to clear space from it?

Well, your “500 GB” drive would only have 465GB free when it was empty, so I don’t know if that’s affecting your calculations.

Also, things in the Recycle Bin aren’t gone from the drive, they’re just in the Recyle Bin folder, so they still take up the same amount of space… you have to empty the trash to clear the space.

Also, there’s a difference between the size of the file and the size of space that it takes up on the disk.  Windows calls this “Allocation Units”.  Each file must occupy a whole number of Allocation Units, and one allocation unit may not be shared between 2 or more files.  So, depending on the size of the Allocation Units and the sizes of your files, this can eat up space too.

For example, if the drive was formatted with 4K Allocation units, then each file must be stored in 4K blocks.  Even if the file is 1 byte (or zero bytes), it will still occupy 4096 bytes on the disk… or if the file is 4097 bytes (4096 + 1) then it will occupy 8192 bytes on the disk (4096 * 2), etc…

So, if you have a lot of files, and especially a lot of small files, the partial Allocation Units can also be eating up your available space.

As an extreme example, your 500GB drive would be “full”, with no remaining free space, if you filled it with enough files of 0K size  (although it’d take about 120 million of them, with 4K Allocation Units), despite the fact that the sum of the file sizes is still zero.

Thank you. I did empty the recycling bin. I think your explanation about the size of the Allocation units is probably correct - I automatically back up everything. If I send items smaller than 4K to the recycling bin and empty it, should it open up 4K of space? Is there a way to reformat the drive so it small items do not hog space? I though I read about this as a possible solution. Mine is now in FAT32?. Thanks again.