CCTV Storage Calculation for Business: A Practical Guide

Why your 8-camera office is probably storing the wrong amount of video

A 40-person logistics firm in Peenya called us in March 2025 because they had 14 cameras, a 4TB NVR, and 11 days of retention. Their insurance surveyor wanted 90 days. The finance head wanted to know why a camera system needed a storage upgrade at all. We rebuilt the setup, and the bill came to ₹1.68 lakh including a 24TB usable Synology RS2423+ NAS, four Seagate SkyHawk AI 8TB drives, and labour. The old NVR went to a second site.

The mistake was not the hardware. The mistake was that nobody had done the bitrate maths before buying. The installer had said "8TB is plenty for 14 cameras" because that is what installers say. The consultant who quoted 90 days had assumed 1080p at 4 Mbps for every camera, which would have needed 38TB and a ₹4.5 lakh quote. The actual cameras were 4MP Hikvision ColorVu units running H.265+ at 15 fps, and their true bitrate averaged 2.1 Mbps. The right number sat between the two guesses, and neither party had bothered to calculate it.

This is the single most common storage sizing failure I see across 1200-plus deployments. Three parties — the installer, the IT team, and the vendor — each produce a number, none of them match, and the business owner signs off on whichever is cheapest. Then footage gets overwritten before the retention period, or storage sits at 18% utilisation for three years.

This article is the calculation. It is the same process our engineers use when we size systems for clients through our security and surveillance services, written out so you can either audit a vendor's quote or build the spreadsheet yourself.

The four variables that actually determine your storage

Every CCTV storage number comes from four inputs. Get these wrong and the whole estimate collapses.

1. Bitrate per camera — measured in megabits per second (Mbps). This is the master variable. Everything else scales from it.
2. Number of cameras — including future additions. If you are likely to reach 30 cameras in two years, size for 30 now.
3. Recording hours per day — typically 24, but motion-triggered recording can cut effective hours by 40-60% in low-traffic areas.
4. Retention days — how many days of footage the business genuinely needs, not how many the vendor happens to have configured.

The formula that ties them together:

Storage (GB) = (Bitrate in Mbps × Number of cameras × Hours per day × 3600 × Retention days) ÷ (8 × 1024)

Or, the shortcut version every CCTV engineer carries in their head:

Storage (GB) ≈ Bitrate (Mbps) × Cameras × Days × 10.8 (for 24×7 recording)

That 10.8 is the multiplier for continuous 24-hour recording. To sanity-check it: 1 Mbps for 1 day is 10.8 GB. That is 1 megabit × 86,400 seconds ÷ 8 = 10,800 megabytes. Correct.

Everything downstream — codec, resolution, frame rate, motion detection, scene complexity — feeds into that first number, the bitrate. So the rest of this article is largely about pinning bitrate down honestly.

Bitrate by resolution, frame rate, and codec

Vendors publish bitrate ranges that span 4× between top and bottom. "2-8 Mbps" for a 4MP camera is not a specification; it is a shrug. The actual bitrate depends on the codec, frame rate, and how much motion is in the scene.

Codec is the biggest lever

H.264 is the baseline. H.265 roughly halves the bitrate for the same perceived quality. H.265+ (Hikvision's variant) and Smart H.265+ (Dahua's) add scene-adaptive compression that can shave another 30-50% in low-motion scenes — but the savings evaporate when there is constant movement. A busy warehouse aisle at peak shift sees maybe 15% savings from H.265+; an empty corridor overnight sees 60%.

Do not believe a vendor who quotes H.265+ at its best-case savings for a scene with continuous motion. Assume the middle of the range.

Resolution and frame rate

Higher resolution increases bitrate roughly linearly with pixel count, if all else is equal. A 4MP camera is 2.25× the pixels of 1080p, and typically 1.6-2× the bitrate at the same frame rate and codec.

Frame rate matters less than people think for storage, but it matters for motion sharpness. Dropping from 25 fps to 15 fps cuts bitrate by roughly 25-35%. Dropping to 10 fps saves more but makes fast-moving footage mushy — bad for a gate camera trying to read number plates.

Here are the numbers I would actually use for 2026 planning. These assume H.265, typical Indian office and industrial scenes, 25°C ambient, and mixed motion.

These are planning figures, not vendor marketing. A 4MP Hikvision ColorVu DS-2CD2347G2-LU running H.265+ at 15 fps in a standard office corridor logs around 1.4-1.8 Mbps in our deployments. In a car park at dusk with constant vehicle movement, the same camera pushes 2.6-3.0 Mbps. Plan for the higher end and you will not be disappointed.

What drives bitrate up beyond resolution

Four things murder your storage budget silently:

• Wide dynamic range (WDR) — needed at gates and glass-front entrances. Adds 15-25% to bitrate because the encoder has more tonal information to compress.
• Colour night vision — the ColorVu and DarkFighter models. Adds 10-20% because the encoder is handling chroma the mono version discarded.
• High motion scenes — traffic, conveyor belts, retail floors during peak hours. Up to 60% higher than an empty scene.
• Smart analytics channels — people counting, intrusion detection, ANPR. The metadata stream itself is small, but if analytics trigger extra recording on a second stream, budget another 20%.

A realistic 4MP outdoor camera at a factory gate (ColorVu, WDR on, 25 fps, H.265+) sits at 2.8-3.4 Mbps. That is not the 1.4 Mbps in the table. The table is a floor, not a target.

Working out retention days: the compliance anchor

Retention is where most storage sizing arguments start, because people confuse legal requirements with operational preferences.

What Indian law actually says

The DPDP Act 2023 does not mandate a minimum CCTV retention period. It requires that personal data be retained only as long as necessary for the purpose it was collected for, and Section 8(7) requires erasure once the purpose is served. That cuts both ways: it does not give you a licence to keep footage forever without reason, and it does not force you to delete at 30 days.

CERT-In's April 2022 directions (mandatory under Section 70B(6) of the IT Act) require that ICT system logs — which include CCTV systems connected to a network — be maintained for 180 days within Indian jurisdiction. This applies to "service providers, intermediaries, data centres, body corporate and Government organisations." A 15-person trading company is arguably not covered; a 200-seat BPO with a data network almost certainly is. The practical advice: if your CCTV system sits on the same network as your business systems and you have any regulator-facing activity, plan for 180 days.

Sector overrides matter more than the general law:

Do not take a vendor's word on retention requirements. Take your auditor's word, and if you have none, take your lawyer's.

The operations-driven reasons to keep more

Even without a legal floor, three operations reasons push retention past 30 days:

• Theft investigations. A stock discrepancy at a warehouse is typically noticed during month-end stock count. That can be 25-35 days after the theft. A 30-day retention window catches it if you are lucky. A 45-day window catches it always.
• Employee disputes. HR escalations, cash-handling disputes, and POSExceptions surface weeks after the event. 60 days is the practical minimum for any business handling cash.
• Insurance claims. Motor claims, fire, and burglary often take 45-90 days to file formally after the incident, and the insurer will want footage.

Most of our clients settle at 60 or 90 days. A few go to 180 for CERT-In alignment. Very few genuinely need a year, and when they insist, we usually push back and ask what investigation took 11 months to launch.

RAID for NVRs: a short, blunt guide

Consumer-grade NVRs and cheap 4-bay NAS boxes often ship with JBOD or RAID 0 as the default. Both are wrong for CCTV, and here is why.

• JBOD (Just a Bunch of Disks). Each drive is independent. If a 6TB drive dies, you lose the ~6TB it held. In a 4-drive system, that is 25% of your retention gone instantly.
• RAID 0 (striping). Data is spread across drives for speed. Lose one drive, lose everything. Great for scratch disks, catastrophic for CCTV. CCTV does not need stripe speed — sequential writes at 1-60 Mbps total are trivial for a single modern disk.
• RAID 1 (mirroring). 50% usable capacity. Fine for a small 2-drive NVR but wasteful at scale.
• RAID 5 (striping with parity). N-1 usable. Survives one drive failure. Writes suffer during rebuild, and during a rebuild, a second drive failure is your whole archive gone. For 4 drives, usable capacity is 75%.
• RAID 6 (double parity). N-2 usable. Survives two drive failures. Slower writes (significant parity computation) but for CCTV you do not care. This is what you want for anything above 4 drives. Usable capacity is 67% for 6 drives, 75% for 8 drives.
• RAID 10. N/2 usable, survives one drive from any mirror pair. Fast. Expensive. Rarely worth it for CCTV since write speed is not the bottleneck.

Use surveillance-grade drives, not desktop drives

Seagate SkyHawk and SkyHawk AI, Western Digital Purple and Purple Pro — these are built for 24×7 write-heavy workloads and have a workload rating of 180-550 TB/year. A desktop drive (WD Blue, Seagate Barracuda) is rated for 55 TB/year and will die within 18-24 months in an NVR. The price difference is ₹2,500-4,000 per 8TB drive. Buy the surveillance drives. Every time.

For a critical system — say a 40-camera factory covering a bonded warehouse — I would use SkyHawk AI (the AI variant handles the smart analytics stream without choking) and RAID 6 on a proper NAS. For a small 8-camera office, Hikvision's own NVR with two WD Purple drives in RAID 1 is fine.

NVR versus NAS for storage

We deploy both. For a 12-camera retail chain, an NVR is right. For a 60-camera IT campus that wants the cameras to authenticate against Active Directory and integrate with door access, a Synology RS2423+ or QNAP TS-855X running Milestone XProtect Express+ is the correct answer.

If you are not sure which side of the line your business sits on, this is exactly the sizing question our security and surveillance team handles during pre-sales.

Worked example 1: 8-camera small office

Let us make this concrete.

The business: An 18-person CA firm in Indiranagar. Office on the second floor of a commercial building, shared lobby, one entrance, a small server room, a reception, and a back door to a service corridor. They want to see who came in, protect the server room, and settle client-petty-cash disputes.

The system:

Total bitrate: 17.0 Mbps.

Retention target: 90 days (they handle cash and wanted to be safe).

Storage = 17.0 × 8 (no — use the formula properly)

Let me do it right. Storage in GB = (17.0 Mbps × 86,400 seconds × 90 days) ÷ (8 × 1024)

= (17.0 × 86,400 × 90) ÷ 8,192

= 132,192,000 ÷ 8,192

= 16,138 GB ≈ 15.8 TB usable

Add 15% overhead for filesystem, logs, and the NVR's own operating space. That gives 18.1 TB usable.

Design: A 4-bay Synology DS923+ with four 8TB WD Purple drives in RAID 6 gives 16TB usable. Not quite enough. Four 10TB drives in RAID 6 gives 20TB usable — fits with headroom. Cost: Synology DS923+ at ₹72,000 (2026 pricing), four WD Purple 10TB at ₹22,500 each = ₹90,000, plus installation and configuration ₹8,000. Total ₹1.70 lakh excluding cameras and NVR software licence.

If they had accepted a cheaper 8TB single-drive NVR: 8TB usable, 45 days retention, no redundancy. That setup would have cost ₹48,000. It would also have lost all footage the day the drive failed, which for a CA firm holding client cash is not a risk worth ₹80,000.

Worked example 2: 32-camera retail chain

The business: A four-outlet garment retail chain, ~120 staff total, based out of Jayanagar, with branches in Malleshwaram, BTM Layout, and one in Mysuru. Central monitoring at the Jayanagar HO.

The system (per outlet, averaged):

Per outlet: 8 cameras. Four outlets: 32 cameras total.

Total bitrate per outlet: (2×3.2) + (4×2.6) + (1×2.8) + (1×2.0) = 6.4 + 10.4 + 2.8 + 2.0 = 21.6 Mbps

Total across four outlets: 86.4 Mbps

Retention: 60 days. Retail theft and staff disputes are the drivers; the insurer asked for 45 days minimum but the HR head wanted 60.

Storage per outlet = (21.6 × 86,400 × 60) ÷ 8,192 = 111,974,400 ÷ 8,192 = 13,668 GB ≈ 13.3 TB usable

Plus 15% overhead: 15.3 TB usable per outlet

Design per outlet: A Synology DS1522+ 5-bay NAS with four 8TB Seagate SkyHawk drives in RAID 6 sits at 16TB usable. That fits. Cost: DS1522+ at ₹68,000, four SkyHawk 8TB at ₹18,500 each = ₹74,000, install ₹6,000 → ₹1.48 lakh per outlet.

Across four outlets: ₹5.92 lakh for edge storage. Alternatively, they could centralise storage at Jayanagar with a larger NAS and stream the remote outlets over MPLS or SD-WAN — but for four outlets, the WAN bandwidth and licence costs (Milestone, Nx Witness charge per camera) make edge storage cheaper until you cross roughly eight outlets. We have run the numbers repeatedly, and the break-even is around 8-10 sites.

A cheaper option: replace the 4MP ColorVu units in stockrooms with 2MP H.265 cameras at 1.2 Mbps and drop stockroom retention to 30 days. Saves roughly 3TB per outlet, ₹18,000 in drives per outlet, and pushes total storage to ₹5.2 lakh. That is a real trade-off — stockrooms are usually where shrinkage happens, so cutting retention there is the wrong saving.

Worked example 3: 60-camera manufacturing plant

The business: A 180-person injection-moulding plant in Bommasandra. Perimeter, shop floor, dispatch, and gates.

Total bitrate = (16×3.0) + (20×2.4) + (8×3.2) + (4×4.0) + (8×2.0) + (4×2.2) = 48 + 48 + 25.6 + 16 + 16 + 8.8 = 162.4 Mbps

That is a heavy system. Retention target: 180 days (CERT-In alignment — the company has a data centre and is arguably in scope).

Storage = (162.4 × 86,400 × 180) ÷ 8,192 = 2,525,363,200 ÷ 8,192 = 308,271 GB ≈ 301 TB usable

Add 15% overhead: 346 TB usable

Now we have crossed the threshold where NVRs and small NAS boxes are irrelevant. You need a proper storage platform.

Recommended design: Two Synology RS4021xs+ units (each a 16-bay 3U rackmount), 16 drives each, in a Synology High Availability cluster. Each unit filled with 16TB Seagate SkyHawk AI drives in RAID 6.

Usable per unit: 16 drives − 2 parity = 14 drives × 16TB = 224TB. Some Synology RAID 6 formatting overhead knocks this to about 213TB usable per unit. Two in HA still give 213TB usable (HA is mirroring at the unit level, not disk level).

That is not 346TB. So we need three units, or drives with higher capacity. Three units: 639TB usable raw before overhead — overkill. Two units in a scale-out configuration with 22TB drives: 14 × 22TB = 308TB usable per unit, in a Synology SA3400D scale-out pair = 308TB usable with HA. That fits with a bit of headroom.

Or: reduce retention to 90 days and use a single 16-bay unit.

Option A — 90-day retention, single NAS: Storage needed = 173TB usable (150TB after overhead, plus 15%). One Synology RS4021xs+ with sixteen 16TB SkyHawk AI drives in RAID 6. Cost: RS4021xs+ at ₹4.15 lakh, 16 drives at ₹34,500 each = ₹5.52 lakh, RAM upgrade and setup ₹60,000. Total ₹10.27 lakh.

Option B — 180-day retention, HA pair: Storage needed = 346TB usable. Two Synology SA3400D units, each with twelve 22TB SkyHawk AI drives in RAID 6 (usable per unit: 10 × 22 = 220TB; two units in HA = 220TB, which is short). Add drive shelves. Or run a three-node scale-out. Realistic cost: ₹32-38 lakh with drives, shelves, and setup.

This is the point where most plant managers take a deep breath and go with Option A, 90 days. That is usually the right call. Unless CERT-In genuinely applies to your business, 180 days is expensive insurance. And on the ground, most investigations of a manufacturing incident are done inside 30 days.

The other lever: reduce bitrate on perimeter cameras from 25 to 15 fps overnight. Perimeter is empty from 8pm to 6am. That alone saves roughly 20,000 GB over 180 days — about 20TB of the requirement.

The failure story that taught us to measure first

In late 2024, we took on a client — a mid-sized logistics company in Nelamangala, 90 staff, operating a yard and a bonded warehouse. They had a 5-year-old CCTV system with 22 cameras, all H.264, 8TB of NVR storage across two Hikvision DS-7716NI units. Retention had dropped to 9 days over the years because more cameras had been added to a system that was never resized.

We specified a proper replacement: 22 cameras upgraded to Hikvision 4MP ColorVu, H.265+, 60-day retention. Our initial calculation used the planning table figures — around 2.2 Mbps per camera for a mixed indoor/outdoor deployment. Total bitrate 48.4 Mbps. Storage: (48.4 × 86,400 × 60) ÷ 8,192 = 30.6TB, plus 15% = 35.2TB. We deployed a Synology RS3621xs+ with eight 10TB SkyHawk drives in RAID 6, giving 60TB usable — generous headroom.

Four months later, the client's IT team called to say storage was at 68% and climbing. The retention was effectively 48 days, not 60.

We pulled the analytics. Actual average bitrate was 3.4 Mbps per camera, not 2.2. The reason: the yard cameras were covering a working goods yard with continuous vehicle movement, at night under floodlights with WDR active. The colour night vision was working overtime, and the H.265+ savings were closer to 20% than 50% because there was motion in almost every frame. Real bitrate was 74.8 Mbps across the system, not 48.4.

Actual storage needed for 60 days: (74.8 × 86,400 × 60) ÷ 8,192 = 47.3TB, plus overhead = 54.4TB. We had 60TB usable, so we just barely fit — but only because we had over-provisioned by luck. If we had deployed the original 4-drive 40TB unit, we would have been at 60TB shortfall and a full-site camera swap mid-project.

Cost of the fix: ₹42,000 in additional drives, two engineer-days, and a lesson. Cost of the mistake, if we had not over-provisioned by accident: roughly ₹3.8 lakh in a second round of drives and chassis.

The lesson: measure actual bitrate on a pilot camera for 48 hours before finalising the design. On any outdoor site with vehicles, add 40-50% to the planning table numbers. Every site, without exception, is more motion-heavy than the person specifying it expects.

We now deploy a single pilot camera and pull the actual bitrate before quoting. It has saved the same mistake four times.

Bandwidth, RAM, and the things people forget

Storage is the headline, but three other numbers break CCTV deployments when they are ignored.

Network bandwidth

Each camera's bitrate adds up on the network. For continuous recording, the NVR pulls the mainstream from every camera. If you have 32 cameras at 2.4 Mbps each, that is 76.8 Mbps of sustained traffic. On a 1Gbps Ethernet link, that is fine — you are at 7.7% utilisation. But the NVR-to-storage link and the camera-to-NVR link both carry this. A single gigabit port per NVR is fine up to roughly 60 cameras at generous bitrates. Beyond that, use 10Gbe uplinks or multiple NVRs.

If remote viewing matters, budget for a substream — Hikvision and Dahua both offer a second stream at 512 Kbps-1 Mbps. That is what the mobile apps and remote users should pull, not the full 4K mainstream.

RAM in the NVR/NAS

Rule of thumb: 2GB RAM per 16 cameras minimum, 4GB recommended. Hikvision's DS-7700 series comes with 4GB base; Synology surveillance stations want 8GB minimum and often benefit from 16GB. Insufficient RAM causes dropped frames before it causes anything else, which is a silent failure — recordings look fine until you play them back during an investigation.

Processor and VMS sizing

If you are running VMS software (Milestone, Nx Witness, Genetec), the CPU is the constraint. A 60-camera install at 1080p mainstream needs roughly 6-8 modern CPU cores. At 4K, double it. A low-end Intel i3 will not handle 40 cameras at 4K even if the storage is huge.

UPS for the NVR/NAS

Bangalore power blips are frequent — BESCOM grid faults plus diesel generator changeover windows leave a 15-60 second gap where the NVR sees no power. Budget for a 1-2 kVA online UPS (not line-interactive) for every NVR/NAS. A NAS doing a backup write when power drops can corrupt its array. ₹18,000-₹35,000 depending on the model. Do not skip it.

The ₹ angles: what this actually costs in 2026

Hardware prices moved around in 2024-2025. Hard drive pricing spiked in early 2025 and settled through the year. These are the figures we are quoting in 2026.

All figures ex-GST. CCTV systems for business are taxed at 18% GST as security equipment (HSN 8525 for cameras, 8471 for storage servers).

For a small 8-camera office, all-in (cameras, NVR/NAS, drives, install, UPS) typically lands at ₹1.9-2.6 lakh including GST.

For a 30-40 camera mid-size business, all-in is ₹5.5-8.5 lakh depending on camera mix, retention, and RAID choice.

For a 100-camera enterprise, ₹18-30 lakh is normal. Multi-site adds WAN, VMS licensing, and central management.

If the numbers surprise you, the surprise is usually because the vendor quoted storage and cameras but not UPS, not installation labour, not the network switch port costs, and not the annual maintenance. If you want a formal budget scoping, our team can work through it — talk to us.

Sizing tools, spreadsheets, and what to avoid

Vendors publish online calculators. Some are useful; most are marketing.

Useful ones:

• Hikvision's storage calculator (verify the codec defaults — it often assumes worst case)
• Axis Communications' Axis Site Designer (industrial grade, very accurate, but requires knowing the Axis camera models)
• Synology NVR Selector (quick, decent)

What to avoid:

• Any calculator that does not let you set the codec. If it locks to H.264 at 4 Mbps for every camera, it is a selling tool not a sizing tool.
• Any calculator that does not distinguish indoor from outdoor. Outdoor footage compresses worse because of sky, weather, and motion.
• Any calculator from a company that also sells storage and whose results always land just under the size of their standard SKU. This is real. We have seen quotes where the vendor's calculator mysteriously produced numbers that matched their 8TB SKU no matter how the inputs changed.

Best practice: build the spreadsheet yourself. Columns for camera position, resolution, fps, codec, motion level (low/medium/high), and estimated bitrate. Sum, apply retention, add 15% overhead, then shop around. It takes an hour and it is the difference between a system that lasts four years and one you are upgrading in eighteen months.

FAQ

How much storage do I need for 16 CCTV cameras? For 16 cameras at 4MP, H.265+, 20 fps, mixed motion, expect about 30-34 Mbps total. At 30-day retention that is roughly 8.5TB usable; at 90 days, 25TB usable. Add 15% overhead. A 4-bay NAS with four 10TB drives in RAID 6 (20TB usable) covers 60 days; a 6-bay with six 10TB drives in RAID 6 (40TB usable) covers 90 days with headroom.

Is 1TB enough for a CCTV system? For one camera at 4MP H.265+ at 2 Mbps, 1TB gives about 58 days of retention. For four cameras, it is 14 days. For eight cameras, seven days. 1TB is not enough for any commercial deployment beyond two or three cameras with very short retention.

Should I use RAID for my NVR storage? Yes for any business system. RAID 1 for two drives, RAID 6 for four or more. Avoid RAID 0 entirely — no redundancy, complete loss on a single drive failure. Avoid JBOD for the same reason. RAID is not backup, but it is the difference between losing one drive's worth of footage and losing your entire retention window.

H.264 or H.265 for CCTV storage? H.265, without hesitation, for new deployments in 2026. It roughly halves storage requirements for the same perceived quality. Compatibility is no longer an issue on current NVRs and NAS platforms. The only reason to use H.264 today is if you are adding cameras to a legacy NVR that cannot decode H.265.

How many days of CCTV footage should a business keep? 60-90 days is the practical default for most Indian businesses. Check your sector's regulator: banking and insurance typically require 90 days, telecom 1 year, and CERT-In direction requires 180 days for in-scope ICT systems. Below 30 days is a real risk for theft, HR disputes, and insurance claims.

Why does my CCTV storage fill up faster than the calculator predicted? Almost always because the actual bitrate is higher than the assumed bitrate. Reasons: more motion than expected, WDR or colour night vision active, smart analytics enabled, or H.265+ savings smaller than the vendor's best-case figure. Pull actual bitrate from the NVR's camera status page after 48 hours and adjust.

What to do next

Open your NVR or VMS interface and pull three numbers right now: total incoming bitrate in Mbps, current retention in days, and percentage of storage used. Compare retention days to what your business actually needs. If the number is under 45, you have an upgrade coming.

If you want a sizing exercise done properly — with a pilot camera measurement, sector-specific retention advice, and a design that will not need replacing in two years — get in touch. We will quote a system against measured bitrates, not vendor marketing tables. Start with a call.