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RAID Capacity Calculator

Estimate usable storage for common RAID levels.

RAID is not backup. Real usable capacity can vary by filesystem, formatting and vendor units.
How it works

Estimate usable storage for common RAID layouts.

Comparison method: RAID 0 = all drives. RAID 1 = one drive. RAID 5 = (nāˆ’1) drives. RAID 6 = (nāˆ’2) drives. RAID 10 ā‰ˆ half the drives.

Worked example

Four 4 TB drives in RAID 5 gives about 12 TB before formatting and filesystem overhead.

Common mistakes
  • Thinking RAID is a backup.
  • Ignoring rebuild risk and filesystem overhead.
  • Mixing different drive sizes without checking behaviour.
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