The RAID Capacity Calculator is designed to simplify this process by calculating total usable capacity based on the number of drives, drive size, and RAID level. It also helps you understand redundancy, fault tolerance, and storage efficiency, ensuring your setup meets your performance and data protection needs.
RAID Capacity Calculator
What Is RAID?
RAID stands for Redundant Array of Independent Disks. It combines multiple hard drives or SSDs to improve:
- Performance – Faster read/write speeds
- Redundancy – Protects against disk failures
- Capacity – Aggregates multiple drives into one logical volume
Different RAID levels balance these factors differently. The most common RAID levels include:
- RAID 0 – Striping, no redundancy, maximum performance
- RAID 1 – Mirroring, full redundancy, usable capacity = half
- RAID 5 – Striping with parity, single-drive failure protection
- RAID 6 – Striping with dual parity, tolerates two disk failures
- RAID 10 (1+0) – Mirrored stripes, combination of RAID 1 and 0
RAID Capacity Formulas (Plain Text)
The usable capacity of a RAID array depends on the RAID level, number of drives (n), and individual drive size (s).
1. RAID 0 (Striping)
No redundancy. Total capacity:
Capacity = n × s
2. RAID 1 (Mirroring)
Full redundancy, mirrors drives. Usable capacity:
Capacity = s
(Only one drive’s worth of storage is usable.)
3. RAID 5
Striping with single parity:
Capacity = (n − 1) × s
(n must be ≥ 3)
4. RAID 6
Dual parity:
Capacity = (n − 2) × s
(n must be ≥ 4)
5. RAID 10
Mirrored stripes:
Capacity = (n ÷ 2) × s
(n must be even)
How to Use the RAID Capacity Calculator
Using the calculator is simple:
Step 1: Enter the Number of Drives
Input the total number of disks in your array.
Step 2: Enter Drive Size
Enter the capacity of each drive (GB or TB).
Step 3: Select RAID Level
Choose RAID 0, 1, 5, 6, or 10. Each level has specific redundancy rules.
Step 4: Click Calculate
The calculator instantly outputs:
- Total usable storage capacity
- Total raw storage capacity
- Storage efficiency
- Fault tolerance level
Step 5: Review Results
Understand how much space you get versus the total physical disk space and the number of drives you can lose without data loss.
Example Calculations
Example 1: RAID 0
4 drives, 2TB each:
Capacity = 4 × 2 = 8TB usable
No redundancy. Fast, but losing one drive loses all data.
Example 2: RAID 1
2 drives, 2TB each:
Capacity = 2TB
Full redundancy. One drive mirrors the other.
Example 3: RAID 5
5 drives, 1TB each:
Capacity = (5 − 1) × 1 = 4TB usable
Can survive 1 drive failure.
Example 4: RAID 6
6 drives, 2TB each:
Capacity = (6 − 2) × 2 = 8TB usable
Can survive 2 drive failures.
Example 5: RAID 10
4 drives, 1TB each:
Capacity = (4 ÷ 2) × 1 = 2TB usable
Can survive 1 drive failure per mirrored pair.
Benefits of Using a RAID Capacity Calculator
✔ Accurate Planning
Avoid overestimating or underestimating storage.
✔ Data Protection Awareness
Understand redundancy and fault tolerance of different RAID levels.
✔ Efficient Storage Use
Maximize usable capacity while maintaining reliability.
✔ Saves Time
Instantly calculates capacity for any number of drives and RAID levels.
✔ Ideal for Home or Enterprise
Works for NAS, SAN, workstations, and server storage planning.
Helpful Tips for RAID Setup
- Choose the Right RAID Level – Balance between speed, capacity, and redundancy.
- Use Identical Drives – Different sizes can reduce efficiency.
- Check Drive Reliability – Enterprise drives are better for RAID setups.
- Monitor Array Health – Replace failed drives promptly.
- Consider Hot Spares – Some RAID controllers allow standby drives.
- Backup Data Regularly – RAID is not a substitute for backups.
- Use ECC Memory if Possible – Reduces errors in RAID arrays.
- Plan for Expansion – Leave room for adding additional drives.
20 Frequently Asked Questions (FAQs)
1. What is a RAID Capacity Calculator?
A tool to calculate usable storage and redundancy for RAID setups.
2. Which RAID levels does it support?
RAID 0, 1, 5, 6, and 10.
3. How do I calculate RAID 5 capacity?
Capacity = (n − 1) × drive size.
4. How is RAID 6 different from RAID 5?
RAID 6 can tolerate 2 drive failures; RAID 5 only 1.
5. What is RAID 0 good for?
Maximum speed, no redundancy.
6. What is RAID 1 used for?
Full redundancy; mirrors one drive to another.
7. How much usable space do I get in RAID 10?
Half of the total drive space is usable.
8. Can I mix drive sizes in RAID?
Not recommended; capacity is limited by smallest drive.
9. Does RAID replace backups?
No, RAID protects against disk failure, not accidental deletion or corruption.
10. What happens if a RAID 5 drive fails?
The array continues to function; data is reconstructed when replaced.
11. How do I increase RAID capacity?
Add more drives (if controller supports it) or use larger drives.
12. What is storage efficiency?
Ratio of usable capacity to total physical capacity.
13. How many drives can I lose in RAID 6?
Up to 2 drives.
14. How many drives can I lose in RAID 5?
Only 1 drive.
15. Is RAID 0 safe?
No; one drive failure causes total data loss.
16. Can I calculate total raw storage?
Yes; raw storage = number of drives × individual drive size.
17. Does RAID 10 require an even number of drives?
Yes, minimum 4 drives.
18. Is RAID used in home NAS?
Yes, for redundancy and performance.
19. Does RAID improve speed?
RAID 0 and RAID 10 improve read/write performance; others may vary.
20. Can I use SSDs and HDDs together in RAID?
Technically yes, but performance and efficiency will be limited.