RAID Calculator
Calculate usable capacity, fault tolerance and speed for RAID 0, 1, 5, 6, 10 and more.
5.0 (1 rating)Enter your values to see the result.
Drive makers count 1 TB as 1,000 GB, while Windows shows capacity in TiB (1,024 GiB), so formatted drives look about 9% smaller.
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Understand the method, inputs and limits behind your result.
- Formula
- Usable capacity depends on drive count and RAID level: RAID 0 uses all drives; RAID 1 mirrors; RAID 5 reserves one drive; RAID 6 reserves two; RAID 10 uses half the drives. Mixed-drive arrays are constrained by the smallest drive.
- Variables
- RAID level: RAID 0 (striping), RAID 1 (mirroring), RAID 5 (single parity), RAID 6 (double parity), RAID 10 (striped mirrors), RAID 50, RAID 60, JBOD (spanning)
- Number of disks
- Size of each disk
- Unit: TB, GB
- Units
- Use the units shown beside each input. Counts and ratios are dimensionless unless labeled otherwise.
- Example
- Four 4 TB disks in RAID 5 give 12 TB usable and survive one disk failure. The same disks in RAID 10 give 8 TB but rebuild faster.
- Assumptions
- Drive makers count 1 TB as 1,000 GB, while Windows shows capacity in TiB (1,024 GiB), so formatted drives look about 9% smaller.
- Source
- ToolzHive calculation guide and calculator implementation. External reference verification is pending.
- Last reviewed
- Review date not yet recorded.
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Clear instructions
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How to use the RAID Calculator
Calculate usable capacity, fault tolerance and speed for RAID 0, 1, 5, 6, 10 and more.
- 1 Choose the RAID level.
- 2 Enter the number of disks and the size of each disk.
- 3 Compare usable capacity, redundancy and fault tolerance.
Example and practical tips
Four 4 TB disks in RAID 5 give 12 TB usable and survive one disk failure. The same disks in RAID 10 give 8 TB but rebuild faster.
Frequently asked questions
Is RAID a backup?
No. RAID keeps a system running when a disk fails, but it does not protect against deletion, ransomware, fire or controller failure.
Why does my system show less space?
Operating systems count in tebibytes (1,024-based), while disks are sold in terabytes (1,000-based), so 12 TB shows as about 10.9 TiB.
Practical guides
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How to Use RAID Calculator
Calculate usable storage, fault tolerance, efficiency and speed gains for RAID 0, 1, 5, 6, 10, 50, 60 and JBOD from the number and size of disks.
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