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NAS Storage Calculator

Estimate NAS raw, usable, reserved, and effective capacity from drive count, drive size, RAID mode, reserve, and compression.

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Inputs

TB

Your values stay on this device.

Results

Effective Usable Capacity
Raw Capacity96
RAID Usable Capacity72
Fault ToleranceTwo drives

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Assumptions

  • Uses decimal TB drive ratings.
  • Compression ratio is entered as an effective planning factor.
  • No device information is stored.

Sensitivity preview

Drive Count -10%: Effective Usable Capacity 56.1 TB

Drive Count Current: Effective Usable Capacity 67.32 TB

Drive Count +10%: Effective Usable Capacity 67.32 TB

Formula: Raw TB = drive count * drive size. RAID usable TB depends on mode. Effective usable TB = RAID usable TB * compression ratio * (1 - reserve percent / 100).

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About this NAS Storage Calculator

NAS capacity is less than raw disk capacity once protection, filesystem reserve, snapshots, and compression assumptions are considered.

Who this calculator is for

  • IT teams sizing file servers.
  • Small businesses planning NAS purchases.
  • Admins comparing RAID layouts.

When to use it

  • Estimate usable NAS capacity.
  • Compare RAID 5, RAID 6, RAID 10, mirror, and single disk layouts.
  • Add reserve and compression assumptions.

How to use this calculator

  1. Enter drive count and drive size.
  2. Choose RAID/protection mode.
  3. Set reserve and compression or dedupe ratio.
  4. Review raw, usable, reserved, and effective capacity.

Key assumptions

  • Uses decimal TB drive ratings.
  • Compression ratio is entered as an effective planning factor.
  • No device information is stored.

Accuracy and testing

Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.

View accuracy page

How this calculator works

Raw TB = drive count x drive size. RAID usable TB depends on protection level. Effective TB = RAID usable TB x compression ratio x (1 - reserve percent).
Raw TB = drive count * drive size. RAID usable TB depends on mode. Effective usable TB = RAID usable TB * compression ratio * (1 - reserve percent / 100).

Inputs explained

Drive count and size

Physical disks and nominal capacity per disk.

RAID mode

Protection layout that determines usable capacity and fault tolerance.

Reserve and compression

Operational reserve reduces capacity; compression or dedupe can increase effective logical capacity.

Understanding your results

Use effective usable capacity for planning but leave extra room for snapshots, rebuilds, and filesystem behavior.

Example scenarios

Eight-drive NAS

8 x 12 TB in RAID 6 gives roughly 72 TB before reserve, snapshots, filesystem formatting, and dedupe assumptions.

Key Features

  • Instant Calculation
  • Private & Secure
  • Mobile Optimized

Tips & Best Practices

  • Keep reserve space for snapshots and rebuild safety.
  • Use RAID 6 or better for larger arrays.
  • Validate vendor capacity because filesystem overhead varies.

Frequently Asked Questions

Is this the same as the RAID calculator?
It builds on RAID capacity and adds NAS planning assumptions such as reserve space and compression.
Why does usable capacity differ from advertised disk capacity?
Protection, reserved space, snapshots, filesystem metadata, and decimal/binary unit differences reduce practical capacity.
Is any infrastructure data stored?
No. The calculation runs locally in your browser and does not upload your inputs.