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NAS RAID Capacity Calculator

Calculate usable NAS RAID capacity, parity overhead, drive-failure tolerance, TB-to-TiB conversion, and reserved storage.

NAS PLANNING TOOL

Calculate RAID usable capacity

Estimate usable storage, parity overhead, drive-failure tolerance, and the capacity your operating system will display.

Choose the protection and performance layout.
Between 2 and 60 identical drives.
Use the manufacturer’s advertised capacity.
NAS drives are normally advertised in decimal TB.
Optional filesystem, snapshots, and free-space reserve.

How the estimate works

The calculator assumes every drive has the same usable size. In mixed-drive arrays, each drive is normally limited to the size of the smallest drive.

  • RAID is not backup: it improves availability but does not protect against deletion, ransomware, corruption, theft, or NAS failure.
  • TB and TiB differ: drive vendors use decimal TB, while many operating systems display binary TiB.
  • Keep free space: NAS performance and snapshot behavior can degrade when a storage pool is nearly full.