A Synology NAS Calculator is a practical tool designed to help users estimate the usable storage capacity of a Synology NAS (Network Attached Storage) system before purchasing or configuring hard drives. Whether you are setting up a personal backup solution, media server, surveillance storage system, or business file-sharing environment, understanding available storage capacity is essential.

Many users purchase multiple hard drives for their NAS devices but often overlook the impact of RAID configurations on actual usable storage. Different RAID levels provide varying levels of redundancy and fault tolerance, which directly affect the amount of storage space available.

This Synology NAS Calculator helps users determine how much usable storage they will receive based on:

• Number of drives
• Drive size
• RAID type
• Total raw capacity
• Usable storage capacity
• Redundancy allocation

By calculating these values beforehand, users can make informed purchasing decisions and avoid unexpected storage limitations.

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What Is a Synology NAS?

A Synology NAS is a dedicated storage device connected to a network that allows multiple users and devices to access files from a centralized location.

Common uses include:

• File storage
• Data backup
• Media streaming
• Security camera recording
• Cloud synchronization
• Team collaboration
• Virtual machine storage

Synology NAS devices support various RAID configurations that improve data protection and system reliability.

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What Does the Synology NAS Calculator Do?

The calculator estimates storage utilization based on your selected RAID setup.

It calculates:

Total Raw Storage

The combined capacity of all installed drives.

Formula:

Total Raw Storage = Number of Drives × Drive Capacity

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RAID Overhead

The amount of storage reserved for data protection.

RAID configurations use part of the storage for redundancy, reducing usable space.

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Usable Storage Capacity

The actual storage available for your files after RAID protection is applied.

Formula:

Usable Capacity = Raw Capacity − RAID Reserved Capacity

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Required Inputs

The Synology NAS Calculator requires only a few important inputs.

Number of Drives

Enter the total number of hard drives installed in the NAS.

Example:

• 2 Drives
• 4 Drives
• 6 Drives
• 8 Drives
• 12 Drives

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Drive Capacity

Specify the storage size of each drive.

Examples:

• 1 TB
• 2 TB
• 4 TB
• 8 TB
• 12 TB
• 16 TB
• 20 TB

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RAID Type

Select the desired RAID configuration.

Common options include:

• RAID 0
• RAID 1
• RAID 5
• RAID 6
• RAID 10
• SHR (Synology Hybrid RAID)

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Supported RAID Calculations

RAID 0

RAID 0 provides maximum storage capacity and performance but no fault tolerance.

Formula:

Usable Capacity = Number of Drives × Drive Size

Example:

4 × 4 TB drives

Usable Storage:

16 TB

Fault Tolerance:

0 drives

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RAID 1

RAID 1 mirrors data across drives.

Formula:

Usable Capacity = Size of One Drive

Example:

2 × 8 TB drives

Usable Storage:

8 TB

Fault Tolerance:

1 drive

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RAID 5

RAID 5 dedicates one drive's capacity for parity.

Formula:

Usable Capacity = (Number of Drives − 1) × Drive Size

Example:

4 × 10 TB drives

Usable Storage:

30 TB

Fault Tolerance:

1 drive

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RAID 6

RAID 6 reserves the equivalent of two drives for parity.

Formula:

Usable Capacity = (Number of Drives − 2) × Drive Size

Example:

6 × 10 TB drives

Usable Storage:

40 TB

Fault Tolerance:

2 drives

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RAID 10

RAID 10 combines mirroring and striping.

Formula:

Usable Capacity = Total Capacity ÷ 2

Example:

4 × 8 TB drives

Usable Storage:

16 TB

Fault Tolerance:

Multiple drives depending on mirror pairs

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Synology Hybrid RAID (SHR)

SHR is Synology’s flexible RAID technology.

Benefits include:

• Better drive utilization
• Mixed drive size support
• Easier upgrades
• Simplified management

For equal-sized drives, SHR behaves similarly to RAID 5.

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How to Use the Synology NAS Calculator

Using the calculator is simple.

Step 1

Enter the number of drives.

Example:

4

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Step 2

Enter the drive size.

Example:

8 TB

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Step 3

Choose the RAID type.

Example:

RAID 5

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Step 4

Click Calculate.

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Step 5

View results including:

• Raw storage
• RAID overhead
• Usable storage
• Redundancy level

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Example Calculation

Suppose you plan to install:

• 4 hard drives
• 8 TB each
• RAID 5 configuration

Raw Capacity

4 × 8

= 32 TB

RAID 5 Reserved Capacity

1 × 8

= 8 TB

Usable Capacity

32 − 8

= 24 TB

Result

• Raw Storage: 32 TB
• Usable Storage: 24 TB
• Redundancy: 8 TB
• Fault Tolerance: 1 Drive

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Why Storage Capacity Matters

Storage planning helps prevent future upgrades and downtime.

Benefits include:

Better Budget Planning

Estimate storage needs before buying drives.

Avoid Capacity Shortages

Ensure enough space for future growth.

Optimize RAID Selection

Balance storage efficiency and data protection.

Improve Backup Planning

Know how much backup space will be available.

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Common Synology NAS Use Cases

Home Media Server

Store movies, music, and photos.

Recommended RAID:

RAID 5 or SHR

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Small Business File Server

Centralized document storage.

Recommended RAID:

RAID 5 or RAID 6

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Surveillance Storage

Continuous video recording.

Recommended RAID:

RAID 6

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Backup Repository

Long-term backup storage.

Recommended RAID:

SHR

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Tips for Choosing the Right RAID

Choose RAID 0 When

• Performance is critical
• Data loss is acceptable

Choose RAID 1 When

• Simple redundancy is needed
• Only two drives are available

Choose RAID 5 When

• Storage efficiency is important
• Moderate protection is acceptable

Choose RAID 6 When

• Maximum protection is required
• Large drive arrays are used

Choose SHR When

• Flexible expansion is desired
• Mixed drive sizes are planned

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Advantages of Using a Synology NAS Calculator

Faster Planning

Instantly estimate storage needs.

Accurate Capacity Estimates

Reduce configuration mistakes.

Easier Hardware Selection

Determine the correct drive sizes.

Better Upgrade Decisions

Plan future expansions efficiently.

Enhanced Data Protection Awareness

Understand RAID redundancy before deployment.

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FAQs with Answers (20)

1. What is a Synology NAS Calculator?

A tool that estimates usable NAS storage capacity based on drive count, drive size, and RAID type.

2. Why is usable storage less than total storage?

RAID redundancy reserves some storage for data protection.

3. Does RAID improve performance?

Some RAID levels can improve read and write performance.

4. What is SHR?

SHR stands for Synology Hybrid RAID, Synology's flexible RAID system.

5. Is SHR better than RAID 5?

For many users, SHR offers easier expansion and better flexibility.

6. Can I mix drive sizes in SHR?

Yes, SHR supports mixed drive capacities.

7. Does RAID replace backups?

No. RAID provides redundancy, not a backup solution.

8. Which RAID is best for home users?

RAID 5 or SHR are commonly recommended.

9. How many drives are required for RAID 5?

A minimum of three drives.

10. How many drives are required for RAID 6?

A minimum of four drives.

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

The array continues operating until the failed drive is replaced.

12. What happens if two drives fail in RAID 5?

Data loss may occur.

13. Can RAID 6 survive two drive failures?

Yes, RAID 6 can tolerate two simultaneous drive failures.

14. Is RAID 10 faster than RAID 5?

Generally, RAID 10 offers better performance.

15. How accurate is the calculator?

It provides reliable estimates based on standard RAID formulas.

16. Can I upgrade my NAS later?

Yes, many Synology systems support expansion.

17. Why does Synology report slightly different capacity values?

Manufacturers and operating systems use different storage measurement methods.

18. Is SSD storage supported?

Yes, Synology NAS systems can use SSDs.

19. Can the calculator estimate backup requirements?

It can help estimate available storage for backup planning.

20. Who should use a Synology NAS Calculator?

Home users, IT administrators, businesses, photographers, videographers, and anyone planning NAS storage.

Conclusion

A Synology NAS Calculator is an essential planning tool for anyone building or upgrading a Synology storage system. By calculating raw capacity, RAID overhead, and usable storage space, users can make smarter purchasing decisions and ensure their NAS meets both current and future storage requirements. Whether you are setting up a home media server, business file storage solution, surveillance system, or backup repository, understanding storage efficiency is crucial. Using a Synology NAS Calculator helps eliminate guesswork, improves capacity planning, and ensures the right balance between storage performance and data protection for long-term reliability and growth.