Or else you should just realise how the manufactures calculate their GBs.
Manufaturer
160 GB = 160 x 1000 x 1000 x 1000
Computer system
(160 x 1000 x 1000 x 1000) / (1024 x 1024 x 1024) = 149 GB.
Now do the math, and you will know how much storage space you have from your future TB drive.
