The formula: cameras × daily write rate × retention days = raw storage, then add for redundancy. As a working guide, allow 8–15 GB per day for an HD camera, 15–25 GB for 2K and 30–50 GB for 4K on continuous recording. So ten 4K cameras kept for 30 days needs roughly 12 TB — before any RAID overhead. The two levers that change the answer most are retention (how long you keep footage) and whether you record continuously or on detection, which alone can cut requirements by more than half.
The calculation, step by step
- List your cameras by resolution. Not every camera needs to be 4K — mixing resolutions by purpose is the single easiest saving.
- Apply a daily write rate to each: roughly 8–15 GB/day for HD (1080p), 15–25 GB for 2K, 30–50 GB for 4K on continuous recording.
- Multiply by your retention target in days.
- Add RAID overhead — parity or mirroring consumes capacity that is not available for footage.
- Add headroom. Sites add cameras. Size for where you will be in two years, not today.
A worked example: eight 4K cameras and twelve HD cameras, kept 30 days.
8 × 40 GB = 320 GB/day, plus 12 × 12 GB = 144 GB/day → 464 GB/day.
Over 30 days that is about 14 TB of footage — so with single-parity redundancy you would be
shopping for roughly 18–20 TB of raw capacity.
What actually changes file size
The ranges above are wide because five things move the number, and they compound:
| Factor | Effect | Practical note |
|---|---|---|
| Resolution | Largest single factor | 4K is roughly three times HD for the same scene |
| Frame rate | Close to linear | Halving 30 fps to 15 fps roughly halves storage; 15 fps is ample for most evidence |
| Scene activity | Can double or halve it | A busy road frontage writes far more than a stockroom, because modern codecs only encode change |
| Compression | Significant | H.265 is substantially more efficient than H.264 at the same quality |
| Lighting | Underestimated | Infrared night footage is noisier, and noise compresses badly — night can cost more than day |
Continuous vs detection-based recording
This is the biggest lever you control, and it is a genuine trade-off rather than a free saving.
| Mode | Storage | Risk | Best for |
|---|---|---|---|
| Continuous | Baseline (100%) | None — everything is recorded | Entrances, tills, gates, anywhere evidence quality matters |
| Motion-triggered | Often 30–50% of continuous | Can miss the moment before a trigger; false triggers in wind or rain | Yards, corridors, low-traffic areas |
| Smart detection (person, vehicle) | Lowest | Only records what it classifies | Areas where only people or vehicles matter |
A sensible middle path used on most professional installations: continuous on the cameras that matter — entrances, points of sale, gates, cash handling — and detection-based on the rest. You keep the evidentiary value where you would actually need it and halve the storage everywhere else.
How long should you keep footage?
Retention is a business decision, not a technical one, and it is usually the number people pick last and should pick first. Common practice:
- 7–14 days — homes and small shops, where incidents are noticed almost immediately.
- 30 days — the most common business default. Long enough that an incident noticed on a monthly review is still recoverable.
- 60–90 days — sites with insurance requirements, disputes that surface late, or staff and customer incident processes that take weeks.
- Longer — where a specific obligation applies.
Practically, it is far cheaper to buy larger drives now than to add capacity later, so where the requirement is genuinely uncertain, size to the longer figure.
Worked examples
| System | Daily write | 30 days | 60 days | 90 days |
|---|---|---|---|---|
| 4× HD (home) | ~48 GB | ~1.4 TB | ~2.9 TB | ~4.3 TB |
| 8× 4K (small business) | ~320 GB | ~9.6 TB | ~19 TB | ~29 TB |
| 16× 4K (medium site) | ~640 GB | ~19 TB | ~38 TB | ~58 TB |
| 30× 4K (large site) | ~1.2 TB | ~36 TB | ~72 TB | ~108 TB |
| 70× 4K (enterprise) | ~2.8 TB | ~84 TB | ~168 TB | ~252 TB |
All figures are usable footage capacity on continuous recording at 40 GB/day per 4K camera — add redundancy on top, and reduce substantially if you use detection-based recording on the quieter cameras.
RAID overhead: raw is not usable
Drive redundancy protects footage when a disk fails — and disks in surveillance systems fail more often than desktop disks, because they are writing continuously. The cost is capacity.
| Protection | Usable capacity | Survives |
|---|---|---|
| No protection | 100% | Nothing — one failure loses the array |
| Single parity | Roughly (n−1)/n | One drive failure |
| Two parity drives | Roughly (n−2)/n | Two simultaneous failures |
| Mirroring | 50% | One drive per pair |
On a 16-bay recorder, two parity drives cost about an eighth of raw capacity — cheap insurance on a system that may be your only record of an incident. Worth knowing what that looks like in practice: sixteen 18 TB drives is 288 TB raw, and around 252 TB usable with two parity drives.
Choosing drives: size, type and compatibility
- Surveillance-rated, always. These drives are built for continuous write loads and for multiple drives vibrating in one chassis. Desktop drives are not, and fail early in this duty.
- Fewer, larger drives beats more, smaller ones. Bay count is fixed at purchase; drive size is the only thing you can grow later. Filling every bay with small disks now means replacing them all to expand.
- Check the compatibility list. Manufacturers publish supported drive lists, and compatibility is physical as well as electronic — some drives lack the mounting screw positions the caddies expect.
- Buy matched drives where you can. Mixed sizes in a protected array typically waste the difference.
- Budget for a spare. One drive on the shelf turns a failure into a ten-minute job rather than a week's wait.
How many bays — and which recorder
Once you know usable terabytes, the bay count follows. Divide your requirement by realistic drive size, then add bays for redundancy:
| Usable requirement | Typical configuration | Suitable recorder class |
|---|---|---|
| Up to ~4 TB | 1 drive | Compact recorder or a gateway that records — see Dream Machines |
| ~5–20 TB | 3–4 drives with parity | 4-bay recorder |
| ~20–40 TB | 5–7 drives with parity | 7-bay recorder |
| ~40–250 TB | 8–16 drives with parity | 16-bay enterprise recorder — see the ENVR guide |
| Beyond that | Multiple recorders | Several recorders managed together |
Full model-by-model detail is in our NVR comparison, and note that several UniFi gateways record cameras themselves — so small sites often need no separate recorder at all.
Use the official calculator
Before ordering, model your exact configuration with Ubiquiti's capacity calculator at calculator.ui.com. Enter camera counts by resolution, the drive size you intend to fit and your target retention, and it reports how many drives you need — including for gateways that record, not just dedicated recorders. It is the fastest way to sanity-check the estimate you have built by hand.
Ubiquiti also publishes a specification comparison tool at techspecs.ui.com and a storage compatibility list worth checking before buying disks.
Six sizing mistakes
- Sizing on raw capacity instead of usable. RAID overhead is not optional on a system that matters.
- Assuming the camera-count rating means storage is handled. A recorder rated for 70 cameras does not imply it can store 70 cameras for your retention period.
- Forgetting drives are never included. Every recorder ships empty.
- Using desktop drives. They are cheaper per terabyte and fail years earlier under continuous writing.
- Filling every bay with small drives. It leaves no growth path except replacing the lot.
- Picking retention last. It is the number that multiplies everything else — decide it first.
Frequently asked questions
How much storage do I need for security cameras?
Multiply cameras by daily write rate by retention days. As a working guide allow 8-15 GB per day for an HD camera, 15-25 GB for 2K and 30-50 GB for 4K on continuous recording. Ten 4K cameras kept 30 days needs roughly 12 TB of usable footage capacity, before RAID overhead. Retention and recording mode change this more than anything else.
How much storage does a 4K security camera use per day?
Roughly 30-50 GB per day on continuous recording, though the range is wide because frame rate, scene activity, compression and lighting all matter. A camera watching a busy road at 30 fps sits at the top of that range or above; a quiet stockroom at 15 fps sits well below it. Infrared night footage often costs more than daytime because image noise compresses poorly.
How many days of footage should I keep?
Common practice is 7-14 days for homes and small shops, 30 days as the usual business default, and 60-90 days where insurance requirements or slow-surfacing disputes apply. Retention can also be set by your insurer, industry body, licensing conditions or contracts - and privacy considerations cut the other way, since keeping footage longer than needed carries its own obligations. Confirm what applies to your organisation.
Does motion recording really save much storage?
Yes - motion-triggered recording commonly uses 30-50% of continuous, and smart detection filtering for people or vehicles less again. The trade-off is that you may miss the moments before a trigger, and weather can cause false triggers. Most professional installations record continuously on cameras that matter - entrances, tills, gates - and use detection-based recording elsewhere.
What is the difference between raw and usable storage?
Raw is the sum of the drives; usable is what remains after redundancy. Single parity gives roughly (n-1)/n of raw, two parity drives roughly (n-2)/n, and mirroring halves it. For example, sixteen 18 TB drives is 288 TB raw but around 252 TB usable with two parity drives. Always size your retention against the usable figure.
Do I need surveillance-rated hard drives?
Yes. Surveillance drives are designed for continuous write loads and for multiple drives vibrating together in one chassis. Desktop drives are built for intermittent use and fail significantly earlier in this duty - a false economy on a system whose purpose is to have the footage when you need it.
Is it better to buy more small drives or fewer large ones?
Fewer, larger drives. Bay count is fixed when you buy the recorder, but drive size is the only thing you can increase later. Filling every bay with small disks means the only way to expand is replacing all of them. Buy the largest drives your budget allows and leave bays free where possible.
Do security camera recorders come with hard drives?
Generally no - UniFi Protect recorders ship with empty bays, and drives are a separate purchase. Check the manufacturer's storage compatibility list before ordering, because compatibility is physical as well as electronic: some drives lack the mounting screw positions the caddies expect.
Can I add storage to my NVR later?
You can fill empty bays, and you can replace drives with larger ones, though replacing drives in a protected array is a staged process rather than a swap. What you cannot change is the number of bays - which is why bay count, not initial drive size, is the specification to get right at purchase.
Is there a calculator for camera storage?
Yes. Ubiquiti publishes a capacity calculator at calculator.ui.com where you enter camera counts by resolution, intended drive size and target retention, and it reports how many drives you need - covering gateways that record as well as dedicated recorders. Use it to sanity-check any estimate you build by hand.
Does higher frame rate use more storage?
Yes, close to linearly. Halving frame rate from 30 to 15 fps roughly halves storage. For most evidence purposes 15 fps is entirely adequate - you are identifying people and events, not analysing motion - so it is one of the easiest savings available on cameras where fluid video is not required.
Where can I buy NVRs and surveillance drives in Australia?
ARC IP Networks stocks UniFi Protect recorders and cameras in Australia as an authorised Ubiquiti reseller, with genuine Australian stock, manufacturer warranty, GST tax invoices and fast Australia-wide shipping. Browse recorders and cameras or call 1300 100 440 and we will size it with you.
Buying the UniFi Protect recorder and camera range in Australia
ARC IP Networks is an authorised Ubiquiti reseller in Australia. We hold deep local stock across the UniFi range, so most orders ship the same or next business day from Australian warehouses — not on a four-week wait from an overseas grey-market seller.
- Genuine Australian stock with full manufacturer warranty and local RMA support
- Competitive pricing — our prices are monitored against the Australian market daily
- Fast Australia-wide shipping, or free pickup from our Melbourne warehouse
- GST tax invoice on every order, with trade accounts available
- Volume and project pricing for integrators, schools, MSPs and enterprise rollouts
Not sure what your retention target costs in terabytes? Send us your camera list and how long you need to keep footage, and we will size the recorder and drives for you. Talk to our team on 1300 100 440, email info@arcip.com.au, or read more about buying from an authorised Ubiquiti reseller in Australia.
Related reading
- What else you need to buy with a UniFi NVR
- Outgrowing a UniFi Cloud Key: when to move to a rack console
- UniFi Protect NVR comparison: which recorder do you need?
- Ubiquiti ENVR: the complete Australian guide
- How to set up a UniFi Protect NVR — and migrate cameras from an old one
- Best UniFi Protect cameras in Australia
- Buying Ubiquiti in Australia: authorised reseller guide