RAID 5 Calculator
Planning a RAID storage setup? Our RAID 5 Calculator helps you quickly determine usable capacity, parity overhead, storage efficiency, fault tolerance, performance impact, and total cost — all in seconds.
Whether you're building a NAS for home use, configuring a small business file server, or planning enterprise storage, understanding RAID capacity calculations is essential. This tool removes guesswork and gives you accurate, instant results.
What Is RAID 5?
RAID 5 (Redundant Array of Independent Disks) is a storage configuration that uses block-level striping with distributed parity. It requires a minimum of 3 drives and offers a balance of:
- Storage efficiency
- Performance
- Fault tolerance
Unlike RAID 0, which provides no redundancy, or RAID 1, which sacrifices 50% of storage for duplication, RAID 5 distributes parity information across all drives. This means:
- You can lose one drive without losing data.
- You retain higher storage efficiency compared to mirroring.
For users needing even higher protection, RAID 6 allows two drive failures, but at the cost of additional storage overhead.
Why Use a RAID 5 Calculator?
Manually calculating RAID 5 storage metrics can be confusing. You need to consider:
- Total number of drives
- Capacity per drive
- Parity overhead
- Usable storage
- Cost per usable TB
Our RAID 5 calculator automates everything and provides:
✔ Total drives
✔ Data drives
✔ Parity allocation
✔ Raw capacity
✔ Usable capacity
✔ Parity overhead
✔ Storage efficiency (%)
✔ Fault tolerance
✔ Estimated read & write performance
✔ Total cost
✔ Cost per usable TB
This makes it ideal for:
- NAS planning
- Server upgrades
- Budget estimation
- Storage comparison decisions
How to Use the RAID 5 Calculator
Using the tool is simple:
Step 1: Enter Number of Drives
- Minimum: 3 drives
- RAID 5 requires at least three disks for distributed parity.
Step 2: Enter Drive Capacity (TB)
- Input the capacity of a single drive (e.g., 4 TB, 8 TB, 16 TB).
- All drives should ideally be the same size for accurate RAID 5 configuration.
Step 3: Enter Cost per Drive
- Input the price of one drive.
- This helps calculate total investment and cost efficiency.
Step 4: Click “Calculate”
The tool instantly displays:
- Data drives (N - 1)
- Raw capacity (N × drive size)
- Usable capacity ((N - 1) × drive size)
- Parity overhead (1 drive equivalent)
- Storage efficiency percentage
- Read and write performance estimates
- Total system cost
- Cost per usable TB
Step 5: Reset if Needed
Click “Reset” to start a new calculation.
RAID 5 Calculation Formula Explained
Here’s how RAID 5 capacity works:
- Raw Capacity = Number of Drives × Drive Size
- Usable Capacity = (Number of Drives − 1) × Drive Size
- Parity Overhead = Capacity of 1 Drive
- Storage Efficiency = ((Usable ÷ Raw) × 100)
Example:
If you have:
- 4 drives
- 8 TB each
Then:
- Raw Capacity = 32 TB
- Usable Capacity = 24 TB
- Parity Overhead = 8 TB
- Efficiency = 75%
Example RAID 5 Configuration
Let’s say you configure:
- 5 drives
- 10 TB each
- $250 per drive
Results:
- Raw Capacity: 50 TB
- Usable Capacity: 40 TB
- Parity Overhead: 10 TB
- Storage Efficiency: 80%
- Fault Tolerance: 1 drive failure
- Total Cost: $1,250
- Cost per Usable TB: $31.25
This helps you immediately evaluate whether the investment meets your storage and budget goals.
RAID 5 Performance Overview
Read Performance
RAID 5 reads from all drives simultaneously, increasing performance.
Estimated read performance scales with the number of drives.
Write Performance
Write operations require parity calculations, making RAID 5 slower than RAID 0 for writes. However, it remains efficient for most file storage applications.
Best for:
- File servers
- Media storage
- Backup repositories
- Business NAS environments
Not ideal for:
- Heavy database workloads
- High-transaction write environments
Storage Efficiency in RAID 5
Efficiency improves as you add more drives.
| Drives | Efficiency |
|---|---|
| 3 | 66.67% |
| 4 | 75% |
| 5 | 80% |
| 6 | 83.33% |
| 8 | 87.5% |
The more drives you use, the smaller the percentage impact of the single parity drive.
Cost Planning with RAID 5
One of the biggest advantages of this RAID 5 calculator is cost analysis.
It helps you:
- Compare drive sizes
- Evaluate price per TB
- Optimize budget allocation
- Plan storage scaling
Instead of guessing which configuration is most cost-effective, you get instant financial clarity.
Advantages of RAID 5
✔ Tolerates 1 drive failure
✔ Good balance of cost and redundancy
✔ Efficient storage usage
✔ Improved read speeds
✔ Ideal for NAS systems
Disadvantages of RAID 5
✖ Only protects against 1 drive failure
✖ Rebuild times can be long
✖ Write speeds slower than RAID 0
✖ Not ideal for very large drive arrays
Who Should Use This RAID 5 Calculator?
This tool is perfect for:
- IT administrators
- Home lab builders
- Small business owners
- NAS users
- Data hoarders
- System integrators
If you're planning a RAID array, this calculator saves time and prevents costly mistakes.
Frequently Asked Questions (FAQs)
1. What is the minimum number of drives for RAID 5?
RAID 5 requires at least 3 drives.
2. How many drives can fail in RAID 5?
Only one drive can fail without data loss.
3. How is RAID 5 usable capacity calculated?
Usable capacity equals (Total Drives − 1) × Drive Size.
4. Why does RAID 5 lose one drive of capacity?
One drive’s worth of space is used for distributed parity.
5. Is RAID 5 better than RAID 1?
RAID 5 offers better storage efficiency, while RAID 1 offers stronger redundancy per mirrored pair.
6. Does RAID 5 improve speed?
Yes, read performance improves. Write performance is moderately reduced due to parity calculations.
7. Can I mix different drive sizes?
Technically yes, but total capacity will be limited to the smallest drive size.
8. What happens during a rebuild?
Data is reconstructed using parity information when a failed drive is replaced.
9. Is RAID 5 safe for backups?
It provides redundancy but is not a replacement for external backups.
10. How does RAID 5 compare to RAID 6?
RAID 6 tolerates two drive failures but sacrifices more capacity.
11. What is storage efficiency in RAID 5?
It is the percentage of usable storage compared to total raw capacity.
12. Does RAID 5 protect against accidental deletion?
No. RAID protects against hardware failure, not user errors.
13. Is RAID 5 good for home NAS?
Yes, it’s commonly used in home and small office NAS systems.
14. Why is write performance slower?
Parity data must be calculated and written during each write operation.
15. Is RAID 5 still recommended today?
Yes, for balanced storage needs. However, very large arrays may consider RAID 6 for added safety.
Final Thoughts
If you're building or upgrading a storage system, accurate planning is critical. Our RAID 5 Calculator gives you instant insights into capacity, performance, efficiency, and cost — helping you make smarter storage decisions.
Try it now and optimize your RAID 5 configuration with confidence.