RAID Capacity Calculator

Type disk count, size, and level. 6 and 4000 in RAID 5 give 20000.00 GB. 4 and 2000 in RAID 10 give 4000.00 GB. 8 and 8000 in RAID 6 give 48000.00 GB. A layout formula, not a live array.

A layout formula: RAID5 (n-1)×s, RAID10 (n/2)×s, RAID6 (n-2)×s. Not a live array. IOPS sits on IOPS.

Input data

RAID 15: ≥6 disks, even count. RAID 50: ≥6 disks (2 groups). RAID 60: ≥8 disks (2 groups).

Results

Enter data and click Calculate.

How it works

RAID Capacity Calculator in this calculator counts GB from a layout, not from a live array. 6 disks of 4000 in RAID 5 give 20000.00 GB. 4 of 2000 in RAID 10 give 4000.00 GB. 8 of 8000 in RAID 6 give 48000.00 GB. RAID5 = (n-1)×s. RAID10 = (n/2)×s. RAID6 = (n-2)×s.

Field raid-n is the count. Field raid-size is typed GB. Select raid-type in the examples is 5, 10, and 6. (6-1)×4000 = 20000. (4/2)×2000 = 4000. (8-2)×8000 = 48000. Decimal GB, not TiB after 1024.

20000.00 GB does not come from a controller. 4000.00 GB is not mdadm. 48000.00 GB does not know a hot spare. You type n and s. The calculator does not query a live array.

IOPS next door estimates operations from ms. Cache hit ratio counts hits. Here 6 and 4000 in RAID 5 stay 20000.00 GB, the layout formula alone.

Type 6, 4000, and RAID 5, then Calculate. The result is 20000.00 GB. A comma in the size parses. Too few disks for the level breaks the layout. This is not live RAID.

6 and 4000 in 5 give 20000.00 GB. 4 and 2000 in 10 give 4000.00 GB. 8 and 8000 in 6 give 48000.00 GB. Another level at 6 changes 20000.00 GB.

Formula

RAID5 = (n-1)×s; RAID10 = (n/2)×s; RAID6 = (n-2)×s. A layout formula, not a live array.

How to use

  1. Type 6 disks, 4000 GB, and RAID 5.
  2. Click Calculate. The result is 20000.00 GB.
  3. 4 and 2000 in RAID 10 give 4000.00 GB. 8 and 8000 in RAID 6 give 48000.00 GB.
  4. A layout formula, not a live array.
  5. IOPS sits on IOPS.

6×4000 in RAID 5 = 20000.00 GB

A layout formula, not a live array. 6 and 4000 in RAID 5 give 20000.00 GB.

RAID
The raid-type level. 10 at 4×2000 gives 4000.00 GB. A layout formula.
Capacity
Usable GB. 6×4000 in RAID 5 leaves 20000.00 GB. Not mdadm.
Calculator
n, s, and a level. 8 at 8000 in RAID 6 gives 48000.00 GB.

Examples

Example 1

  • 6 disks
  • 4000 GB
  • RAID 5

20000.00 GB

How many GB at 6×4000 in RAID 5? 20000.00 GB. A layout formula, not a live array.

Example 2

  • 4 disks
  • 2000 GB
  • RAID 10

4000.00 GB

What about 4×2000 in RAID 10? 4000.00 GB.

Example 3

  • 8 disks
  • 8000 GB
  • RAID 6

48000.00 GB

What about 8×8000 in RAID 6? 48000.00 GB.

Related calculators

IOPS

IOPS and disk throughput: ms, block KB, and parallelism.

Use calculator →

Storage cost

Storage cost: GB, a price, and months.

Use calculator →

Cache Hit Ratio

Cache Hit Ratio Calculator: hits and misses.

Use calculator →

Data Transfer Time

Data Transfer Time Calculator: MB, Mbps, and efficiency.

Use calculator →

Database Connections

Database Connections Calculator: cores, instances, and an optional cap.

Use calculator →

All IT calculators

Common questions

How many GB at 6×4000 in RAID 5?

20000.00 GB. (6-1)×4000. A layout formula, not a live array.

What about 4×2000 in RAID 10?

4000.00 GB. (4/2)×2000.

What about 8×8000 in RAID 6?

48000.00 GB. (8-2)×8000.

Is this a live array or mdadm?

No. Three fields. The calculator does not read a controller and does not know a spare.

Is 20000.00 GB TiB?

No. Typed decimal GB. 1024 stays outside this calculator.

What about RAID 0 and RAID 1?

RAID 0 is n×s. RAID 1 is s. The examples take 5, 10, and 6.

Does a comma in 4000,5 work?

Yes. Another size at 6 and RAID 5 changes 20000.00 GB.

Where do I time IOPS for those disks?

On IOPS. Here 20000.00 GB from the layout stays.

What if n is too small for the level?

The layout breaks. RAID 5 needs at least 3 disks.

Knowledge sources

The calculator counts bits, bytes or throughput from your numbers. Below are SI and bit definitions (NIST).

Page updated in 2026.

Raw vs usable capacity

Raw capacity = disk count × disk size. Usable capacity = what you can store after mirrors or parity. The gap is the price of redundancy — not “lost” gigabytes, but protection against disk failure.

RAID levels and tradeoffs

LevelIdeaUsable capacityTolerance
RAID 0Stripe — max speed/capacity, zero protection; only for easily rebuilt data100% (n×s)None
RAID 1Mirror~50%1 disk in the pair
RAID 5Single parity(n−1)×s1 disk
RAID 6Double parity(n−2)×s2 disks
RAID 10Stripe + mirror~50%1 disk per mirror pair
RAID 50Striped RAID 5 groups — large arrays wanting more usable space than RAID 10~2×(n/2−1)×s1 disk / group
RAID 60Striped RAID 6 groups — large arrays needing extra rebuild safety~2×(n/2−2)×s2 disks / group

Redundancy, disk failure, and backups

  • After one disk fails, usable capacity does not change — the array runs degraded until you replace the disk and rebuild.
  • During a RAID 5 rebuild there is no spare left — a second failure means data loss. Prefer RAID 6/10 on large disks.
  • RAID ≠ backup. It protects against disk failure, not ransomware, deleted files, or a server-room fire.

Capacity vs resilience

  • Max capacity with 1-disk tolerance — RAID 5.
  • More headroom (2 failures) — RAID 6 (cost: one more disk for parity).
  • Performance + simpler rebuild — RAID 10 (cost: ~50% capacity).

Examples

  • 4 × 1 TB: RAID 5 → usable 3 TB, raw 4 TB; RAID 10 → usable 2 TB, raw 4 TB.
  • 8 × 2 TB: RAID 5 → usable 14 TB; RAID 6 → usable 12 TB (more resilience, less space).
  • 6 × 4 TB, RAID 5 → usable 20 TB, raw 24 TB, 4 TB spent on parity.