RAID Calculator
Calculate usable capacity, fault tolerance and speed for RAID 0, 1, 5, 6, 10 and more.
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.
Continue your work
- Data Storage Converter — Convert between TB, TiB and other units.
- Cubic Feet Calculator — Plan rack or storage room space.
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Clear instructions
Find steps, examples and limitations below.
Use online
Open the tool in a supported web browser.
Free to use
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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.
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