Synology Capacity Calculator -

Number of Drives

Drive Size (TB)

RAID Type

The Synology Capacity Calculator is an essential online planning tool designed for users who want to accurately estimate the usable storage space in a Synology NAS (Network Attached Storage) system. Whether you are building a home media server, small business backup solution, or enterprise storage cluster, understanding how much usable capacity you will actually get from your hard drives is critical.

Unlike simple storage addition, Synology systems use advanced RAID and SHR (Synology Hybrid RAID) technologies that impact how raw disk capacity is converted into usable space. This calculator helps users avoid confusion, plan upgrades, and ensure optimal storage efficiency before investing in hardware.

With increasing demand for data backup, video surveillance storage, and multimedia libraries, this tool becomes extremely valuable for IT professionals, businesses, and home users alike.

What is the Synology Capacity Calculator Used For?

The Synology Capacity Calculator is designed to help users:

Estimate usable storage in a Synology NAS
Compare RAID levels (RAID 0, RAID 1, RAID 5, RAID 6, RAID 10)
Understand SHR (Synology Hybrid RAID) storage behavior
Plan disk upgrades and expansion
Determine redundancy and fault tolerance
Avoid overestimating available storage space

It eliminates guesswork and provides a realistic view of how much storage will actually be available after redundancy overhead.

Key Inputs Required

To ensure accurate calculations, the tool requires the following inputs:

1. Number of Drives

The total number of hard drives installed or planned in the NAS.

2. Drive Capacity

Capacity of each drive (e.g., 2TB, 4TB, 8TB, etc.). In mixed setups, multiple values may be supported.

3. RAID Type or SHR Mode

Users must select a storage configuration such as:

RAID 0 (performance, no redundancy)
RAID 1 (mirroring)
RAID 5 (single-disk redundancy)
RAID 6 (dual-disk redundancy)
RAID 10 (performance + redundancy)
SHR / SHR-1 / SHR-2 (Synology Hybrid RAID options)

4. Optional Expansion Settings

Some advanced versions may include:

Hot spare drives
Mixed drive sizes
Future expansion planning

Expected Outputs

The Synology Capacity Calculator provides clear, actionable results including:

1. Usable Storage Capacity

The actual usable space after RAID/SHR overhead.

2. Redundancy Level

Indicates how many drives can fail without data loss.

3. Storage Efficiency

Percentage of raw capacity usable for data storage.

4. RAID Breakdown

Explanation of how storage is distributed across disks.

5. Expansion Projection

Estimated capacity after adding additional drives.

Calculation Logic (How It Works)

The tool uses RAID-based mathematical logic:

RAID 0

Total usable = sum of all drives
No redundancy

RAID 1

Usable = size of smallest drive
Mirrors data across disks

RAID 5

Usable = (Number of drives - 1) × drive size
1 drive used for parity

RAID 6

Usable = (Number of drives - 2) × drive size
2 drives used for parity

RAID 10

Usable = 50% of total raw capacity
Combination of mirroring + striping

SHR (Synology Hybrid RAID)

Dynamic allocation based on drive sizes
Optimized space usage compared to traditional RAID

These formulas ensure realistic predictions of usable storage.

How to Use the Synology Capacity Calculator

Using the tool is simple and user-friendly:

Step 1: Enter Number of Drives

Select how many hard drives you plan to use.

Step 2: Input Drive Size

Provide the storage capacity of each drive.

Step 3: Select RAID or SHR Type

Choose the RAID configuration that matches your system goals.

Step 4: Click Calculate

The tool processes the inputs and instantly generates results.

Step 5: Review Output

Analyze usable storage, redundancy, and efficiency metrics.

Practical Example

Example Setup:

4 drives
Each drive = 4TB
RAID 5 configuration

Calculation:

Usable capacity = (4 - 1) × 4TB = 12TB

Result:

Total raw capacity: 16TB
Usable storage: 12TB
Redundancy: 1 drive failure protection

This shows how RAID affects real-world storage availability.

Benefits of Using This Tool

1. Accurate Storage Planning

Prevents underestimating or overestimating storage needs.

2. Cost Efficiency

Helps avoid buying unnecessary extra drives.

3. Better RAID Decisions

Users can compare configurations before setup.

4. Data Safety Awareness

Clearly shows redundancy levels and risk tolerance.

5. Business Optimization

Ideal for server administrators and IT infrastructure planning.

Important Considerations

Drive sizes significantly affect SHR efficiency
RAID 0 is fast but risky due to no redundancy
RAID 6 is safer but reduces usable capacity
SHR is best for mixed drive environments
Real-world formatting reduces usable space slightly

Who Should Use This Tool?

Home NAS users
IT administrators
Video editors managing large files
Surveillance system planners
Cloud backup architects
Small and medium businesses

FAQs with answers (20):

1. What is the Synology Capacity Calculator?

It is a tool that estimates usable storage in Synology NAS systems based on RAID or SHR configuration.

2. Why is usable storage less than total storage?

Because RAID uses part of the storage for redundancy and data protection.

3. Does SHR work like RAID?

Yes, but SHR is more flexible and optimized for mixed drive sizes.

4. What is the safest RAID level?

RAID 6 offers the highest redundancy with protection against two drive failures.

5. Which RAID gives the most storage?

RAID 0 provides maximum storage but no redundancy.

6. Can I mix different drive sizes?

Yes, especially with SHR configurations.

7. Does this calculator include formatting loss?

Most calculators estimate raw RAID capacity, not filesystem overhead.

8. What happens if a drive fails in RAID 5?

Data remains safe but performance may decrease until rebuild.

9. Is RAID 10 better than RAID 5?

RAID 10 is faster, RAID 5 offers more storage efficiency.

10. How accurate is the calculator?

It provides highly accurate theoretical storage estimates.

11. Can I upgrade storage later?

Yes, Synology NAS supports expansion depending on configuration.

12. What is a hot spare drive?

A backup drive that automatically replaces a failed disk.

13. Does RAID increase speed?

Some RAID levels like RAID 0 and RAID 10 improve performance.

14. What is SHR-2?

It is Synology Hybrid RAID with dual-drive failure protection.

15. Is RAID a backup solution?

No, RAID is not a backup; it is redundancy protection.

16. Can I change RAID type later?

Yes, but it may require data migration or rebuild.

17. How many drives do I need for RAID 5?

At least 3 drives are required.

18. What is usable capacity in RAID?

It is the actual storage space available for files.

19. Does drive brand matter?

Not for calculation, but performance and reliability may vary.

20. Why use a Synology calculator?

To plan storage efficiently and avoid costly mistakes.

Conclusion

The Synology Capacity Calculator is a powerful and practical tool for anyone working with NAS storage systems. It removes confusion around RAID and SHR configurations by providing clear estimates of usable storage, redundancy, and efficiency. Whether you are building a personal media server or managing enterprise-level backups, this tool helps you make informed decisions before investing in hardware. By understanding how different RAID levels affect storage capacity, users can balance performance, safety, and cost effectively. Ultimately, it ensures smarter storage planning, reduced risk of data loss, and optimized utilization of every hard drive in your Synology system.