Calculadora de RAID
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
RAID 0: N×S; RAID 1: S; RAID 5: (N-1)×S; RAID 6: (N-2)×S; RAID 10: N/2×S
About this calculator
The RAID Calculator helps determine the usable capacity and overhead (wasted space) for different RAID levels: 0, 1, 5, 6, and 10. Simply enter the number of drives and the individual capacity of each drive (in GB or TB). The tool automatically calculates the total capacity available for data storage, ignoring the space used for redundancy. Overhead is the difference between the total raw capacity (sum of all drives) and the usable capacity.
The calculation follows specific formulas for each level. In RAID 0, usable capacity is N × S (sum of all drives), with no redundancy. In RAID 1, it is only S (one drive), since data is mirrored. In RAID 5, it is (N-1) × S, as one drive is used for parity. In RAID 6, it is (N-2) × S, with two drives for parity. In RAID 10, it is (N/2) × S, as drives are mirrored in pairs and then striped. Overhead is calculated as total raw capacity minus usable capacity.
Use this calculator when planning a storage system, whether for servers, NAS, workstations, or data centers. It is useful for comparing RAID levels, sizing required capacity, and understanding the trade-off between performance, redundancy, and usable space. For example, when choosing between RAID 5 and RAID 6, you can quickly see how many drives are needed to achieve a target capacity.
Cautions: Remember that drive capacities may vary between manufacturers; always use the actual value (not nominal). Additionally, some RAID controllers may reserve space for metadata or bad sector remapping, which slightly reduces usable capacity. This calculator considers only the raw drive capacity, without accounting for additional overhead from file systems or formatting.
Frequently asked questions
What is the difference between RAID 5 and RAID 6 in terms of capacity?
In RAID 5, usable capacity is (N-1) × S, while in RAID 6 it is (N-2) × S. RAID 6 uses two drives for parity, offering more fault tolerance but reducing available space.
Can I mix drives of different capacities in a RAID?
Yes, but the system will use the capacity of the smallest drive as a reference for each member of the array. The extra space on larger drives will be wasted.
What does overhead mean in the context of RAID?
Overhead is the amount of space lost due to redundancy (parity or mirroring). For example, in a 3-drive RAID 5 with 1 TB each, the overhead is 1 TB (one drive dedicated to parity).
Which RAID offers the best performance?
RAID 0 offers the best read and write performance, but has no redundancy. RAID 10 offers good performance with redundancy, but uses half the capacity for mirroring.
How many drives are needed for RAID 10?
RAID 10 requires an even number of drives, at least 4. Usable capacity is half of the total raw capacity.