RAID 5 Storage Calculator
Planning a RAID setup without knowing the exact usable storage can lead to costly mistakes. Whether you’re configuring a home server, business NAS, or enterprise storage system, understanding RAID 5 capacity is essential.
Our RAID 5 Storage Calculator helps you instantly determine:
- Total Raw Capacity
- Usable Capacity
- Parity Overhead
- Storage Efficiency (%)
With just two simple inputs—number of drives and drive size—you can accurately estimate how much storage you’ll actually get from your RAID 5 array.
In this comprehensive guide, you’ll learn how RAID 5 works, how to use the calculator, real-world examples, formulas, best practices, and answers to common questions.
What is RAID 5?
RAID 5 (Redundant Array of Independent Disks Level 5) is a storage configuration that combines:
- Data striping
- Distributed parity
- Fault tolerance
It requires a minimum of 3 drives and can tolerate the failure of one drive without data loss.
Unlike RAID 0 (no redundancy) or RAID 1 (mirroring), RAID 5 offers a balance between:
- Performance
- Storage efficiency
- Data protection
This makes it one of the most popular RAID configurations for NAS systems and business storage environments.
How RAID 5 Capacity Works
When using RAID 5:
- One drive’s worth of space is reserved for parity
- The remaining drives contribute to usable storage
RAID 5 Capacity Formula
If all drives are the same size:
- Total Raw Capacity = Number of Drives × Drive Size
- Parity Overhead = Size of One Drive
- Usable Capacity = (Number of Drives − 1) × Drive Size
- Efficiency (%) = ((Number of Drives − 1) / Number of Drives) × 100
Our RAID 5 Storage Calculator automatically performs these calculations for you.
How to Use the RAID 5 Storage Calculator
Using the calculator is extremely simple:
Step 1: Enter Number of Drives
- Minimum: 3 drives
- Example: 4, 5, 6, etc.
Step 2: Enter Drive Size (GB)
- Input the capacity of a single drive in GB
- Example: 500 GB, 1000 GB, 2000 GB
Step 3: Click “Calculate”
The tool will instantly display:
- Total Raw Capacity
- Usable Capacity
- Parity Overhead
- Storage Efficiency
Step 4: Reset (Optional)
Click the reset button to clear results and start again.
Example RAID 5 Calculation
Let’s walk through a practical example.
Example 1:
- Number of Drives: 4
- Drive Size: 1000 GB
Total Raw Capacity:
4 × 1000 = 4000 GB
Parity Overhead:
1000 GB
Usable Capacity:
4000 − 1000 = 3000 GB
Efficiency:
(3000 ÷ 4000) × 100 = 75%
So with 4 drives, you get 75% storage efficiency.
Example 2:
- Number of Drives: 6
- Drive Size: 2000 GB
Total Raw Capacity:
6 × 2000 = 12000 GB
Parity Overhead:
2000 GB
Usable Capacity:
12000 − 2000 = 10000 GB
Efficiency:
(10000 ÷ 12000) × 100 = 83.33%
As you add more drives, efficiency increases.
Why Use a RAID 5 Calculator?
Manually calculating RAID storage can lead to:
- Incorrect planning
- Underestimating parity overhead
- Budget miscalculations
- Capacity shortages
Our RAID 5 calculator helps you:
✔ Plan storage purchases
✔ Compare RAID configurations
✔ Optimize cost vs redundancy
✔ Avoid wasted storage
✔ Make informed NAS decisions
Understanding RAID 5 Parity
Parity in RAID 5:
- Is distributed across all drives
- Protects against one drive failure
- Reduces total usable storage by one drive
Important: RAID 5 does not protect against:
- Two simultaneous drive failures
- Accidental deletion
- Ransomware
- File corruption
Always combine RAID with proper backups.
RAID 5 Storage Efficiency Explained
Storage efficiency improves as you add more drives.
| Drives | Efficiency |
|---|---|
| 3 | 66.67% |
| 4 | 75% |
| 5 | 80% |
| 6 | 83.33% |
| 8 | 87.5% |
More drives = higher efficiency (but increased rebuild risk).
When Should You Use RAID 5?
RAID 5 is ideal for:
- Small business servers
- NAS systems
- File storage
- Backup repositories
- Media storage
It may not be ideal for:
- High write-intensive databases
- Extremely large drives (long rebuild times)
- Mission-critical systems needing dual redundancy
RAID 5 vs Other RAID Levels
RAID 0
- No redundancy
- 100% efficiency
- High risk
RAID 1
- Mirroring
- 50% efficiency
- Strong redundancy
RAID 5
- Balanced performance
- Single-drive fault tolerance
- Good efficiency
Common RAID 5 Planning Mistakes
- Ignoring parity overhead
- Mixing different drive sizes
- Not accounting for rebuild time
- Skipping backups
- Assuming RAID replaces backup
Our RAID 5 Storage Calculator helps eliminate the first mistake instantly.
Best Practices for RAID 5
- Use identical drive sizes
- Use enterprise-grade drives if possible
- Monitor SMART health
- Keep backups
- Avoid extremely large single arrays
15 Frequently Asked Questions (FAQs)
1. What is the minimum number of drives for RAID 5?
RAID 5 requires at least 3 drives.
2. How much space is lost in RAID 5?
You lose the capacity of one drive for parity.
3. How do I calculate RAID 5 usable capacity?
(Number of drives − 1) × Drive size.
4. Is RAID 5 safe?
It protects against one drive failure, but not multiple failures.
5. Does RAID 5 improve performance?
Yes, especially read performance.
6. Can RAID 5 survive two drive failures?
No. It can only tolerate one failed drive.
7. Why does storage efficiency increase with more drives?
Because parity remains equal to one drive regardless of total drives.
8. Is RAID 5 good for home NAS?
Yes, it’s popular for home and small office NAS setups.
9. Can I mix drive sizes in RAID 5?
Technically yes, but usable space is limited to the smallest drive size.
10. What happens during a rebuild?
Data is reconstructed using parity information.
11. Is RAID 5 better than RAID 1?
It depends—RAID 5 offers better efficiency, RAID 1 offers simpler redundancy.
12. How accurate is this RAID 5 calculator?
It uses the standard RAID 5 capacity formula for precise results.
13. Does RAID 5 protect against ransomware?
No. RAID is not a backup solution.
14. What is parity overhead?
The storage space reserved for redundancy equal to one drive’s capacity.
15. Why use a RAID 5 calculator instead of manual math?
It saves time, prevents mistakes, and helps with fast storage planning.
Final Thoughts
If you’re setting up a RAID array, accurate storage planning is critical. Our RAID 5 Storage Calculator makes it simple to:
- Estimate usable storage
- Understand parity overhead
- Measure efficiency
- Plan hardware purchases confidently
Whether you’re managing enterprise storage or building a personal NAS, this tool ensures you know exactly how much capacity you’ll get before installing your drives.