Shrink partition to exactly fit the underlying filesystem size

Recently i shrinked an ext4 filesystem size to 500GB

df -hFilesystem      Size  Used Avail Use% Mounted on/dev/sda2       493G   64G  404G  14% /

now i want to shrink the partition size to fit exactly to the filesystem size.

I tried to used parted and the resizepart command. The problem is when parted asks for the new size. If i choose 500GB the resulting partition is smaller from 500GB and as a result the underlying filesystem cannot fit on this partition. Any hint on how to do the correct size calculations?