My 3 TB Western Digital Cavier Black was reporting only 746 GB instead of the expected 3 TB (actual 2.7 TB) even using Gparted.
The drive was connected via USB to a circa-2010 Dell Inspiron 530 running Ubuntu 12.04 and to a Dell T320 server also running 12.04.
I knew the problem was not my BIOS because I had previously mounted the 3 TB in a very old Dell running 12.04.
This time, however, I was connecting the drive as an external hard drive via USB. Only when I connected via eSATA Gparted reported 2.7 TB.