Using the Advanced RAID Calculator you can see the exact amount that your array will have using any size of Hard Disk.
ARC Supports the following RAID Levels:
0, 1, 3, 3+0, 4, 5, 6, 0+1, 1+0, 1+0+0, 5+0, 5+1, 6+0, 6+1, BeyondRAID, unRAID, X-RAID, RAID-Z, RAID-Z2, RAID-Z3, RAID DP, SHR, SHR-2.

The app also provides an IOPS calculator to find the type of disk required to achieve the IOPS in the backend as well as a power requirement calculator to help in selecting the appropriate PSU for your setup.

It currently has an extensive database of HDD's but you can also add 1 custom disk with your own specs.

To get access to Alpha & Beta Releases please join this community: https://plus.google.com/communities/101728749503292151303

Please note that EMC & NetApp storage calculations may not be complete or accurate since the manufacturers don't provide detailed information. Please do not forward to me documentation and tools meant for internal use by any company. I am not able to use them legally and you are breaking their TOS.

The app now has the same appearance for any Android version and any Resolution (Including Tablets and Netbooks)