RAID Calculator — Usable Capacity & Fault Tolerance
Enter your RAID level, disk count, and per-disk size to instantly see the usable storage, parity overhead, storage efficiency, and exactly how many drives can fail before data loss.
RAID level
TB
Striping with distributed parity — can lose 1 disk.
- 1
Raw capacity
4 × 4 TB = 16 - 2
Parity overhead (1 disk)
1 × 4 TB = 4 - 3
Usable capacity (RAID 5)
(4 − 1) × 4 TB = 12Distributed parity costs exactly one disk worth of space across all drives.
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RAID levels trade raw capacity for redundancy: RAID 5 gives (n−1)×disk usable, tolerating 1 failure; RAID 6 gives (n−2)×disk, tolerating 2; RAID 1 gives 1×disk, tolerating n−1 failures; RAID 10 gives 50%, tolerating 1 per pair. RAID 0 has no redundancy. Disk sizes are decimal TB; operating systems show binary TiB (1 TB ≈ 0.91 TiB).
Formulė
How this is calculated
RAID (Redundant Array of Independent Disks) combines multiple drives into a logical volume. The level you choose determines the trade-off between capacity, speed and redundancy.
RAID 0 stripes data across all disks for maximum capacity and read/write speed, but offers no redundancy — a single failure destroys all data. RAID 1 mirrors every write to all disks, so any one (or more) can fail as long as one survives; half or more of raw capacity is lost to the mirror copies. RAID 5 distributes parity information across all disks, losing exactly one disk worth of space to parity — at least 3 disks are required and one can fail safely. RAID 6 uses double parity (at least 4 disks), sacrificing two drives worth of space but surviving any two simultaneous failures — safer during the long rebuild times of large drives. RAID 10 (1+0) mirrors pairs and then stripes across them: 50% efficiency, but one disk per mirror pair can fail, making it highly performant and safe. RAID 50 and 60 stripe across two RAID-5 or RAID-6 sub-groups for larger arrays.
Disk sizes here are in decimal terabytes (1 TB = 10¹² bytes), as manufacturers rate them. Operating systems display storage in binary tebibytes (1 TiB = 2⁴⁰ bytes ≈ 1.0995 × 10¹² bytes), so the same disk appears smaller in Windows or Linux. The calculator shows both units. Actual formatted capacity is slightly lower still due to partition tables and filesystem overhead (typically 1–3%).
Dažnai užduodami klausimai
RAID 5 is the most popular for 3–6 drive NAS boxes — it balances usable space with single-drive redundancy. RAID 6 is better if you have 6+ large drives or can afford slower rebuilds. RAID 10 is fastest and most resilient but costs 50% of raw capacity. RAID 0 is only for temporary scratch storage where data loss is acceptable.
Manufacturers rate drives in decimal TB (10¹² bytes), but operating systems display in binary TiB (2⁴⁰ bytes). A 4 TB drive is only 3.64 TiB. The calculator shows both. There is also a small amount of space used by the filesystem itself.
No. RAID protects against hardware failure of one or more disks, but it offers no protection against accidental deletion, ransomware, file corruption, controller failure, or theft. The 3-2-1 backup rule (3 copies, 2 media types, 1 offsite) is still required alongside RAID.
Taip pat žinomas kaip
TG we-Calculate Editorial Team. (2026). RAID Calculator — Usable Capacity & Fault Tolerance [Online calculator]. TG we-Calculate. https://we-calculate.com/lt/calculator/raid-calculator
TG we-Calculate Editorial Team. "RAID Calculator — Usable Capacity & Fault Tolerance." TG we-Calculate. 2026. https://we-calculate.com/lt/calculator/raid-calculator.
TG we-Calculate Editorial Team, "RAID Calculator — Usable Capacity & Fault Tolerance," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/lt/calculator/raid-calculator
@misc{wecalculate_raid_calculator, title = {RAID Calculator — Usable Capacity & Fault Tolerance}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/lt/calculator/raid-calculator}}, year = {2026}, note = {TG we-Calculate} }
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