RAID Capacity
Calculate usable capacity across RAID 0, 1, 5, 6 and 10 configurations.
About RAID Capacity
RAID levels trade capacity for redundancy. RAID 0 offers full capacity but zero fault tolerance. RAID 1 mirrors all data (50% efficiency for 2 drives). RAID 5 uses one drive's worth for distributed parity (n-1 efficiency). RAID 6 uses two drives for double parity. RAID 10 stripes across mirror pairs (50% efficiency).
Formulas
RAID 5 usable capacity
usable = (drives - 1) * drive_size
- n
- Number of drives
- S
- Size per drive
RAID 6 usable capacity
usable = (drives - 2) * drive_size
Worked example
With the default values below, RAID Capacity returns Usable Capacity of 20.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Number of Drivesaccepts 2–100
- 6
- Drive Sizeminimum 0.1 TB
- 4 TB
- RAID Levelone of RAID 0 (Striping), RAID 1 (Mirroring), RAID 5 (Single Parity), RAID 6 (Double Parity), RAID 10 (Stripe of Mirrors)
- RAID 5 (Single Parity)
Results
- Usable Capacity
- 20.00 TB
- Raw Capacity
- 24.00 TB
- Storage Efficiency
- 83.3%
- Parity/Mirror Overhead
- 4.00 TB
- Drive Failures Tolerated
- 1
Step by step
- 1Raw capacity= 24 TB
- 2Usable capacity (RAID ${raidLevel})= 20 TB
- 3Storage efficiency= 83.3%
- 4Drive failures tolerated= 1
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Which RAID level should I choose?
RAID 5 balances capacity and protection for most workloads. RAID 6 is preferred for large arrays (>4 drives) where rebuild times are long enough to risk a second failure. RAID 10 is best for write-intensive workloads needing both performance and redundancy. RAID 0 is only appropriate when data loss is acceptable.
Why is RAID not a substitute for backups?
RAID protects against drive failure only. It cannot protect against accidental deletion, corruption, ransomware, controller failure, or disasters affecting the entire array. Backups protect against all of these scenarios.