RAID Capacity Calculator
Usable capacity and fault tolerance.
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Results update instantly as you type — no submit needed.
Results
- Usable capacity
- 40 TB
- Raw capacity
- 48 TB
- Redundancy overhead
- 16.7%
- Disk failures tolerated
- 1
Quick answer
RAID trades raw capacity for redundancy, with usable space depending on the level chosen.
RAID 5 usable = (n − 1) × disk size
How to use the RAID Capacity Calculator
- 1Enter disk count and size.
- 2Choose the RAID level.
- 3Compare usable capacity with fault tolerance.
Frequently asked questions
Is RAID a backup?
No — it survives disk failure, not deletion, fire or ransomware.
RAID 5 or 6?
Use RAID 6 for disks over 4 TB because rebuild times are long.