RAID Calculator
Calculate the usable storage capacity and fault tolerance for a RAID array.
Enter your values to calculate your result.
Formula
RAID 0: N×Capacity RAID 1: Capacity RAID 5: (N−1)×Capacity RAID 6: (N−2)×Capacity RAID 10: (N÷2)×Capacity
Each RAID level trades off usable capacity for fault tolerance differently: RAID 0 stripes data across all drives with no redundancy; RAID 1 mirrors data, so usable capacity equals a single drive's capacity regardless of how many drives you add; RAID 5 and 6 reserve the equivalent of 1 or 2 drives for parity; RAID 10 mirrors pairs of drives, then stripes across those pairs.
Example
4 drives of 4,000 GB each in RAID 5 give a usable capacity of (4−1) × 4,000 = 12,000 GB, with 1 drive's worth of fault tolerance.
Frequently Asked Questions
Which RAID level should I use?
RAID 0 maximizes capacity and speed but has no fault tolerance (any drive failure loses all data). RAID 1 and 10 prioritize redundancy and read speed at a higher capacity cost. RAID 5 and 6 balance capacity and fault tolerance, with RAID 6 tolerating 2 drive failures at the cost of more overhead. The right choice depends on your priorities — capacity, performance, or how many drive failures you need to survive.
Why does RAID 10 need an even number of drives?
RAID 10 works by first mirroring drives in pairs, then striping data across those mirrored pairs — so drives must be added two at a time.