Free calculator
RAID Capacity Calculator
Eight 16 TB drives give 112 TB usable in RAID 5, 96 TB in RAID 6 and 64 TB in RAID 10. Enter your drive count and size to compare every level side by side, and add the space you need to see which levels hold it and which is the safest.
Free, no sign-up. Runs in your browser.
This web tool uses the RAID rules of the Storage/RAID calculator in the CineMath app, opens on eight 16 TB drives holding 70 TB, shows each level’s fault tolerance beside its name, counts usable space exactly so a target of exactly that size fits, adds the raw capacity in TiB, quotes the space needed and the headroom unrounded, and never offers RAID 0 for a single drive. Save, share and get the Pro tools in the app.
How it works
RAID 0 = n × d
RAID 1 = d
RAID 5 = (n − 1) × d
RAID 6 = (n − 2) × d
RAID 10 = n ÷ 2 × dRAID 1 is a mirror: every drive holds the same data, so it keeps one drive’s worth. Drive sizes are decimal terabytes, as printed on the drive: 1 TB is 10¹² bytes. RAID 0 and RAID 1 need two drives, RAID 5 three, RAID 6 four, and RAID 10 four and an even count.
Where
- n
- Number of drives in the array
- d
- Capacity of one drive (use the smallest if they differ)(TB)
RAID 6 > 10 > 1 > 5With a target, every level whose usable space is at least the target is marked ✓, and the highest-ranked of those is named, with its headroom (usable − needed). RAID 0 is never suggested; when it is the only level that fits, the calculator says so.
TiB = TB × 10¹² ÷ 2⁴⁰
≈ TB × 0.9095A system that counts in binary shows this figure, often still labeled “TB”. The space is all there.
Sizing the target
Size the space you need from the footage, proxies and working files together, then add a margin: an array filled to the last terabyte has nowhere for renders, cache or the reshoot nobody planned. The storage planning guide builds that figure, and the RAID capacity guide covers rebuild time and read-error risk. For long-term copies of finished projects, see LTO tape archiving.
Worked example
70 TB of footage on eight 16 TB drives
- Raw: 8 × 16 TB = 128 TB
- RAID 6: (8 − 2) × 16 TB = 96 TB, which holds 70 TB
- Headroom: 96 − 70 = 26 TB
- In binary units: 96 × 10¹² ÷ 2⁴⁰ = 87.3 TiB
RAID 6 is the safest level that fits: 96 TB usable, 26 TB of headroom, and any two drives can fail.
Quick reference
Usable capacity with 20 TB drives
| Array | Raw | RAID 5 | RAID 6 | RAID 10 |
|---|---|---|---|---|
| 4 drives | 80 TB | 60 TB | 40 TB | 40 TB |
| 6 drives | 120 TB | 100 TB | 80 TB | 60 TB |
| 8 drives | 160 TB | 140 TB | 120 TB | 80 TB |
| 12 drives | 240 TB | 220 TB | 200 TB | 120 TB |
| 16 drives | 320 TB | 300 TB | 280 TB | 160 TB |
| 24 drives | 480 TB | 460 TB | 440 TB | 240 TB |
What each level survives
| Level | Minimum drives | Survives |
|---|---|---|
| RAID 0 | 2 | Nothing: one failed drive loses the array |
| RAID 1 | 2 | All but one drive of the mirror |
| RAID 5 | 3 | Any one drive |
| RAID 6 | 4 | Any two drives |
| RAID 10 | 4, even | One drive in each mirrored pair |
Save, share and get the Pro tools in the CineMath app
CineMath is a free download for iPhone, iPad and Mac, with this calculator built in. In version 1.3, coming soon to the App Store, CineMath Professional saves calculations to your history, shares them as links, and adds the Camera Database and Data Planning.
Questions
How much usable space does RAID 5 give?
One drive less than the array: (n − 1) × drive size. Eight 16 TB drives give 112 TB in RAID 5, 87.5% of the 128 TB raw. RAID 6 gives up two drives instead of one, so the same array holds 96 TB.
Should I use RAID 5 or RAID 6 for video?
RAID 6 for arrays of large drives. A RAID 5 rebuild reads every surviving drive end to end with no redundancy left: for eight 16 TB drives rated at one unrecoverable read error per 10¹⁵ bits, the chance of meeting at least one at the rated maximum is about 59%. RAID 6 still has a second parity to correct it. RAID 5 suits small arrays of smaller drives.
Why does my array show less space than the calculator?
Drive makers count in decimal terabytes and some systems count in binary, often still labeled TB: 96 TB is 87.3 TiB, and one 16 TB drive is 14.55 TiB. The file system also takes a little. The space is all there.
Why does RAID 10 need an even number of drives?
RAID 10 stripes data across mirrored pairs, so every drive needs a partner. It needs at least four drives, keeps half the raw space, and survives one failure in each pair, so it can survive several failures if they hit different pairs.
Why does RAID 1 with eight drives show only one drive’s space?
A RAID 1 mirror writes the same data to every drive, so it holds one drive’s worth however many drives it spans, and survives all but one of them failing. Eight 16 TB drives in RAID 1 hold 16 TB. Mirrored pairs striped together are RAID 10.
Is a RAID array a backup?
No. RAID protects against a drive that stops working, not against a deleted file, corruption written to every drive, a failed enclosure, theft or fire. Count the array as one copy and keep other copies on separate media, one of them off site.