RAID Usable Capacity Calculator — visual relationshipUses the current inputs
The visual explains this calculator’s quantity and updates from the entered values. It does not add measurement accuracy or infer missing physical data.
1EnterProvide the known values
2CalculateResults update automatically
3VerifyReview the details and units
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Calculation result
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Digital information is counted in bits and bytes, then grouped with decimal SI or binary IEC prefixes. Storage, payload rate, duration, copies, compression, and redundancy answer different questions.
Show exactly how selected redundancy and spare assumptions consume capacity while keeping storage-unit conventions and whole-disk constraints visible.
Use the calculator to keep bits separate from bytes, preserve the selected prefix convention, and expose every efficiency, reserve, overhead, copy, or compression assumption.
The relationship
Keep the basis explicit
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.
See the workflow
What the calculator is doing
1Information payload2Apply rate, ratio, or storage model3Read capacity, count, or duration
Worked context
Read the output in context
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.
Interpret with care
Important boundary
A planned transfer or capacity is not a measured device benchmark. Protocol overhead, filesystem behavior, failures, vendor definitions, and real throughput can change the observed result.
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.
Choose the real storage, transfer, media, backup, or archive task first, then enter only the measurements and assumptions that belong to that workflow.
Keep bits and bytes, decimal SI and binary IEC prefixes, rates, durations, counts, reserves, efficiency, overhead, compression, and retention conventions explicit.
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.
