RAID 5 Calculator
RAID 5 stripes data with one drive's worth of distributed parity. It survives one drive failure and keeps the most capacity of any redundant level.
RAID 5 at a glance
- 8 × 16TB in RAID 5 = 112TB usable (101.86 TiB), 88% of raw capacity; survives 1 drive failure.
- 100TB usable from 16TB drives in RAID 5 takes 8 drives (112TB usable).
Identical drives; decimal TB as drives are sold, binary TiB as most operating systems show it; before filesystem overhead. Hot spares are extra drives and add no capacity.
RAID 5 usable capacity by drive count
| Drives | 1.92TB | 3.84TB | 8TB | 12TB | 16TB | 24TB |
|---|---|---|---|---|---|---|
| 3 | 3.84TB | 7.68TB | 16TB | 24TB | 32TB | 48TB |
| 4 | 5.76TB | 11.52TB | 24TB | 36TB | 48TB | 72TB |
| 5 | 7.68TB | 15.36TB | 32TB | 48TB | 64TB | 96TB |
| 6 | 9.6TB | 19.2TB | 40TB | 60TB | 80TB | 120TB |
| 8 | 13.44TB | 26.88TB | 56TB | 84TB | 112TB | 168TB |
| 10 | 17.28TB | 34.56TB | 72TB | 108TB | 144TB | 216TB |
| 12 | 21.12TB | 42.24TB | 88TB | 132TB | 176TB | 264TB |
Usable capacity in decimal TB, before filesystem overhead. — means the drive count is not valid for RAID 5.
RAID 5 formula
Usable capacity = (n − 1) × S. Minimum 3 drives. Fault tolerance: 1 drive. Example: 4 × 8TB = 24TB (21.83 TiB), 75% of raw capacity.
Rebuilds on large drives
After a failure, the controller reads every remaining drive in full to rebuild the lost one. Until that finishes, the array has no redundancy: a second failure, or an unreadable sector on another drive, can lose data. Larger drives take longer to rebuild, which is why many administrators choose RAID 6 for large nearline drives.
Write cost
Each random write costs four disk operations (read data, read parity, write data, write parity). RAID 5 suits read-heavy workloads better than heavy random writes.
16TB drives for this array
In-stock 16TB drives from our catalogue, with the price for the 8 drives in the example above. Hot spares are extra.
- SHD7B06079 - Lenovo 16TB SATA 3.5-Inch Hot-Swap Hard Drive (512e, SED) $247.50 each · 8 drives $1,980.00
- Seagate ST16000NM010G Exos X16 16TB 7200RPM 12Gb/s SAS 256MB Cache 512e Enterprise $429.47 each · 8 drives $3,435.76
- ST16000NM003G - Seagate Exos X16 16TB 7200RPM SATA 6Gb/s 256MB Cache 512e Sed 3.5-inch $447.37 each · 8 drives $3,578.96
- ST16000NM002G - Seagate Exos X16 16TB 7200RPM SAS 12Gb/s 256MB Cache 512e 3.5-inch Hard $450.53 each · 8 drives $3,604.24
- ST16000VN001 - Seagate IronWolf Nas 16TB 7200RPM SATA 6Gb/s 256MB Cache 3.5-inch Hard $468.42 each · 8 drives $3,747.36
- Seagate ST16000NM007H Exos X24 16TB 7200RPM 12Gb/s SAS 512MB Cache 512e 3.5-Inch Hard $478.95 each · 8 drives $3,831.60
- Toshiba MG08ACA16TE 16TB 7200RPM 6Gb/s SATA 512MB Cache 512e 3.5-Inch Hard Drive $468.42 each · 8 drives $3,747.36
- Seagate ST16000NM004G Exos X16 16TB 7200RPM 12Gb/s SAS 256MB Cache Self-Encrypting Drives $500.00 each · 8 drives $4,000.00
Frequently asked questions
How many 16TB drives do I need for 100TB usable in RAID 5?
8 drives, giving 7 × 16TB = 112TB (101.86 TiB), before filesystem overhead.
What is the minimum number of drives for RAID 5?
Three: two drives of data plus one of parity.
Should I use RAID 5 or RAID 6?
RAID 6 gives up one more drive of capacity to survive two failures, which also covers a second failure during a rebuild. For large drives, RAID 6 is the safer default.
How many drives can fail in RAID 5?
One. A second failure before the rebuild finishes loses the array.
RAID calculators by level
- RAID calculator (all levels)
- RAID 0 calculator
- RAID 1 calculator
- RAID 6 calculator
- RAID 10 calculator
- RAID 50 calculator
- RAID 60 calculator
RAID planning guides
- How Many Drives Can Fail in Each RAID Level?
- RAID Hot Spare: What It Does and How It Affects Capacity
- TB vs TiB: Why a 24TB Drive Shows 21.8 TiB
- RAID Write Penalty by Level
- Best RAID Level for 2, 3, 4, 5, 6 or 8 Drives
- RAID 50 vs RAID 60
- RAID 6 vs RAID 60
Related
Updated 2026-10-22.