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Unit Conversions · Digital information

RAID Usable Capacity Calculator

Calculate raw, usable, protected-overhead, hot-spare, and reserved capacity for equal-size RAID 0, 1, 5, 6, and 10 scenarios with valid disk-count rules.

Unit Conversions · Digital information

RAID Usable Capacity Calculator

Private in-browser planning · explicit bits, bytes, units, assumptions, and reconciliation

Calculation result

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Enter valid values to see the result.

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Quick guide

How to use this calculator

  1. Choose the real storage, transfer, media, backup, or archive task first, then enter only the measurements and assumptions that belong to that workflow.
  2. Keep bits and bytes, decimal SI and binary IEC prefixes, rates, durations, counts, reserves, efficiency, overhead, compression, and retention conventions explicit.
  3. Use the companion outputs to reconcile the scenario. Where actual system behavior is unknown, enter measured values or retain the stated limitation instead of treating a plan as a guarantee.

Calculation method

How the raid usable capacity calculator works

Show exactly how selected redundancy and spare assumptions consume capacity while keeping storage-unit conventions and whole-disk constraints visible.

Active disks = installed disks − hot spares. RAID 0 uses all active disks; RAID 1 uses one disk; RAID 5 uses n−1; RAID 6 uses n−2; RAID 10 uses n÷2. Visitor reserve is then subtracted from RAID usable capacity.

Worked example

RAID Usable Capacity example

Six 4 TB disks with one hot spare leave five active disks; RAID 5 provides 16 TB before an entered reserve and consumes 8 TB across parity and the spare.

Active disks = installed disks − hot spares. RAID 0 uses all active disks; RAID 1 uses one disk; RAID 5 uses n−1; RAID 6 uses n−2; RAID 10 uses n÷2. Visitor reserve is then subtracted from RAID usable capacity.

Supported inputs

Precision and limits

Digital-system boundary

This equal-smallest-disk capacity model does not predict reliability, rebuild time, performance, controller behavior, metadata, filesystem overhead, distributed erasure coding, vendor implementation, or data recovery. RAID is not a backup.

Units and precision

One byte is eight bits. Decimal kB, MB, GB and TB use powers of 1,000; binary KiB, MiB, GiB and TiB use powers of 1,024. Calculations retain working precision and round only for display.

Category ownership

This calculator handles neutral information quantity, transfer, storage, media-payload, compression, backup, RAID, or archive arithmetic. Live speed tests, IP addressing, packet engineering, current vendor pricing, security analysis, and physical display sizing belong to other tools.

Privacy

File names and contents are never requested. Entered quantities and results stay in this browser and are not sent to analytics or third parties.

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