How to Calculate CCTV Storage Requirements: Step-by-Step Formula for Bangladesh Facilities

One of the most common — and costly — mistakes in CCTV system design is underestimating storage. A bank branch installs a 24-camera system, sets a 90-day retention requirement to meet Bangladesh Bank guidelines, and discovers six months later that the NVR runs out of space in 60 days. The fix requires additional NVR hardware, an unplanned capital expenditure, and a period of non-compliance.

This mistake is entirely preventable. Calculating CCTV storage requirements is not complicated. It requires a single formula, a few parameters, and the discipline to apply it correctly before purchasing any hardware. This guide walks you through that formula with step-by-step examples for a 16-camera office, a 64-camera factory, and a 200-camera hospital — and explains how to apply it to your specific situation.

The Core Storage Formula

Every CCTV storage calculation reduces to this formula:

Storage (TB) = Bitrate (Mbps) × 3,600 × 24 × Days × Cameras ÷ 8 ÷ 1,000,000,000

Breaking this down:

• Bitrate (Mbps): The data rate of each camera's video stream in megabits per second
• × 3,600: Converts hours to seconds (60 minutes × 60 seconds)
• × 24: Hours in a day
• × Days: Your retention period
• × Cameras: Total number of cameras
• ÷ 8: Converts megabits to megabytes (8 bits per byte)
• ÷ 1,000,000,000: Converts megabytes to terabytes

Or in a simplified form:

Storage (TB) = Bitrate (Mbps) × 0.0108 × Days × Cameras

The constant 0.0108 accounts for the seconds-per-day and bit-to-byte conversions simultaneously.

What Determines Bitrate?

Bitrate — the key input to your storage calculation — is not fixed. It depends on four variables that you must understand and control:

1. Resolution

Resolution is the single biggest driver of bitrate. Higher resolution means more pixels per frame, which means more data to encode and transmit.

These are representative values. Actual bitrate varies with codec and scene complexity.

2. Frame Rate

Frame rate is measured in frames per second (fps). Higher frame rates capture smoother motion but increase bitrate proportionally.

• 5–8 fps: Suitable for slow-moving environments (secure storage rooms, stairwells)
• 12–15 fps: Standard for most CCTV applications — adequate for identifying people and reading events
• 25–30 fps: Required for fast-motion environments (vehicle tracking, sports facilities, manufacturing lines with fast machinery)

Reducing frame rate from 25 fps to 12 fps roughly halves your storage requirement with minimal impact on investigative usefulness for most CCTV applications.

3. Scene Complexity

Scene complexity refers to how much the camera image changes between frames. High-complexity scenes (busy intersections, factory floors with constant movement, outdoor scenes with wind moving trees) generate higher bitrates. Low-complexity scenes (empty corridors, secure storage rooms, underground car parks during off-hours) generate much lower bitrates.

Variable Bit Rate (VBR) encoding, which all modern cameras support, automatically increases bitrate when scenes are complex and reduces it when they are simple. Always use VBR for storage efficiency.

4. Compression Codec

As covered in our H.265 vs H.264 comparison guide, your codec choice dramatically affects storage:

Bangladesh Bank 90-Day Retention Requirement

Worked Example 1: 16-Camera Office (Small Business)

Scenario: A 4-floor corporate office in Gulshan, Dhaka. 16 cameras total: 8 indoor 1080p dome cameras in corridors and common areas, 4 outdoor 1080p bullet cameras at entrances and car park, 4 indoor cameras in the server room and reception area.

Parameters:

• Cameras: 16
• Resolution: 1080p (2MP)
• Frame rate: 15 fps
• Codec: H.265
• Typical bitrate per camera: 2 Mbps
• Retention: 30 days

Calculation:

Storage = 2 Mbps × 0.0108 × 30 days × 16 cameras
Storage = 2 × 0.0108 × 30 × 16
Storage = 10.37 TB

Practical recommendation: Purchase a 16TB NVR storage configuration (allowing for file system overhead, RAID redundancy, and headroom for future camera additions). A single 4-bay NVR with four 6TB surveillance-grade HDDs in RAID 5 provides approximately 18TB usable storage — adequate with room for growth.

Estimated NVR hardware cost: BDT 1.5–2.5 lakh

Worked Example 2: 64-Camera Factory (Mid-Scale Industrial)

Scenario: A readymade garments factory in Ashulia with 64 cameras: 40 indoor cameras covering the production floor, cutting section, and warehouses; 12 outdoor cameras at gates, perimeter, and loading bays; 8 cameras in administrative blocks; 4 cameras in the IT and server room area.

Parameters:

• Cameras: 64
• Resolution: Mixed — 48 cameras at 2MP, 16 cameras at 4MP
• Frame rate: 15 fps
• Codec: H.265+
• Typical bitrate: 1.5 Mbps (2MP), 2.5 Mbps (4MP) with H.265+
• Retention: 30 days (factory compliance) / note 90-day if bank-regulated

Calculation — 2MP cameras (48 units):

Storage = 1.5 Mbps × 0.0108 × 30 × 48 = 23.33 TB

Calculation — 4MP cameras (16 units):

Storage = 2.5 Mbps × 0.0108 × 30 × 16 = 12.96 TB

Total storage required: 36.3 TB for 30-day retention.

Practical recommendation: A rack-mounted NVR with RAID 6 redundancy. Use 12TB enterprise surveillance HDDs (Western Digital Purple Pro or Seagate SkyHawk AI). For 90-day retention: 12 drives of 12TB in RAID 6 provides 120TB usable — sufficient with headroom.

Estimated NVR hardware cost (90-day): BDT 8–14 lakh

Worked Example 3: 200-Camera Hospital (Large Enterprise)

Scenario: A 350-bed private hospital in Dhaka with 200 cameras: 100 indoor corridor and ward cameras at 2MP, 40 cameras at critical areas (pharmacy, ICU entrances, administrative offices) at 4MP, 30 outdoor cameras at 4MP, 20 cameras at vehicle entry, emergency, and ambulance bay at 4K, 10 cameras at server rooms and data storage at 2MP.

Parameters by zone:

• 110 cameras at 2MP, H.265+, 15fps, 1.5 Mbps average
• 70 cameras at 4MP, H.265+, 15fps, 2.5 Mbps average
• 20 cameras at 4K, H.265, 15fps, 8 Mbps average
• Retention: 30 days standard, 90 days for critical areas (pharmacy, ICU, server room)

Calculation for standard 30-day retention (180 cameras):

110 × 1.5 × 0.0108 × 30 = 53.5 TB
70 × 2.5 × 0.0108 × 30 = 56.7 TB
Total: 110.2 TB (30 cameras at standard retention)

Calculation for 90-day retention (20 cameras, 4K):

20 × 8 × 0.0108 × 90 = 155.5 TB

Total storage architecture:

• Standard retention tier: 110 TB
• Extended retention tier: 156 TB
• Combined system total: ~266 TB

Storage architecture recommendation: Two separate NVR systems:

1. Primary NVR system (RAID 6, 120TB usable) for standard 30-day cameras
2. Compliance NVR system (RAID 6, 160TB usable) for 90-day critical cameras

This separation simplifies compliance auditing and allows independent management of each tier.

Estimated NVR hardware cost (complete system): BDT 20–35 lakh

Storage Reference Table

Use this table as a quick reference for common camera configurations.

Based on 15fps recording, VBR encoding with moderate scene complexity.

RAID Storage for Redundancy

Never store critical CCTV footage on a single hard drive without redundancy. Drive failure rates in 24/7 recording systems are meaningful — enterprise HDDs running continuously have an annual failure rate of approximately 1–3%.

RAID Levels for CCTV

For Bangladesh Bank-compliant installations, RAID 6 is the minimum recommendation. The 90-day retention requirement means that a drive failure without redundancy results in a gap in compliance footage that cannot be recovered.

Pro Tip: Alongside RAID, implement a drive health monitoring alert. NVR systems with SMART monitoring can alert administrators when a drive shows early failure indicators, allowing replacement before data loss occurs. Schedule a drive health check with your AMC provider quarterly.

Hybrid Cloud Storage: The Best-of-Both Approach

On-premise NVR storage provides the lowest cost per terabyte and the fastest access to footage. However, it is vulnerable to physical threats: fire, flooding (a serious risk in low-lying areas of Bangladesh during monsoon season), theft, and power surge damage.

A hybrid approach is increasingly used for high-security applications:

• Primary storage: On-premise NVR for all cameras, all retention periods. Fast access, low cost per TB.
• Cloud backup: Critical cameras only (teller counters, vault, ATM, server room) backed up to cloud storage in real time or at scheduled intervals.

This approach protects the most important footage against physical disaster while keeping bandwidth and cloud subscription costs manageable.

Bandwidth requirement for cloud backup: A typical 10-camera critical footage backup at H.265 (average 2 Mbps per camera) requires 20 Mbps sustained upload bandwidth. Verify your ISP connection supports this before specifying cloud backup.

Key Takeaways

• Use the formula: Storage (TB) = Bitrate × 0.0108 × Days × Cameras
• Key bitrate drivers: resolution, frame rate, scene complexity, and compression codec
• H.265+ reduces storage requirements to 20–30% of H.264 for the same quality
• Bangladesh Bank's 90-day retention requirement makes codec selection critical — always specify H.265 or H.265+
• Use RAID 6 for all installations requiring compliance-grade storage redundancy
• Hybrid cloud backup of critical cameras protects against physical disasters
• Always add 20–30% headroom to your calculated storage to accommodate scene complexity variations and future camera additions

Ready to Design Your Storage Architecture?

SSAL's technical team calculates precise storage requirements for your specific facility and designs NVR architectures that meet your compliance obligations. We supply and install Hikvision, Dahua, Bosch, and enterprise RAID NVR systems across Bangladesh with complete maintenance support.

Contact SSAL for a free storage design consultation:

• Phone: +880 1799-986890
• Email: info@smartsafety.com.bd
• Web: www.smartsafety.com.bd
• Office: Youth Tower Level 2, 822/2 Rokeya Sarani, Dhaka-1216

Concerned your current system may not meet Bangladesh Bank's 90-day requirement? Book a compliance audit with our team — we assess your existing storage, calculate the gap, and provide a remediation plan with clear costs and timelines.