How Many CCTV Cameras Does My Building Need? A Floor-Plan-Based Planning Guide

"How many cameras do I need?" is the first question most buyers ask, and it is the question that most vendors answer incorrectly. Some vendors underspecify cameras to win a lower-cost bid, leaving coverage gaps that become apparent only when you need to review an incident. Others overspecify cameras to maximise revenue — running cameras in locations that add no security value.

The correct answer cannot be given without a floor plan, a list of security objectives, and a systematic coverage analysis. Camera count is an output of the design process, not an input to it. This guide explains the methodology for determining exactly how many cameras your building needs — and walks you through a complete worked example for a 3-floor office building.

The Fundamental Principle: Field of View

Every camera has a Field of View (FOV) — the angular width of the scene it can capture. FOV depends on the camera lens (measured in millimetres focal length) and the camera sensor size.

Wide-angle lenses (2.8mm): Approximately 100–110° horizontal FOV. Cover wide areas at short range. Common for corridors and rooms.

Standard lenses (4mm): Approximately 80–90° horizontal FOV. The most common general-purpose specification.

Medium telephoto (6mm): Approximately 50–60° horizontal FOV. Better for longer distances where more detail is needed.

Telephoto (8–12mm): Approximately 30–40° horizontal FOV. Suited for long corridors, gates, and perimeter approaches.

The coverage area of a camera increases with distance from the camera. A 90° FOV camera covers 1.73 metres of width at 1 metre distance, 8.65 metres at 5 metres, and 17.3 metres at 10 metres.

Use this formula to calculate coverage width at a given distance:

Coverage Width = 2 × Distance × tan(FOV/2)

For a 90° FOV camera at 10 metres:

Width = 2 × 10 × tan(45°) = 2 × 10 × 1 = 20 metres

The 20% Overlap Rule

Adjacent cameras should overlap their coverage zones by at least 20%. Overlap serves two purposes:

1. Eliminates blind spots: Without overlap, a person can walk through the gap between two camera zones and be missed.

1. Provides multi-angle evidence: At entry/exit points especially, overlapping cameras provide a second angle that may capture what the primary angle misses (e.g., a person who walks with their face turned away from one camera).

For a corridor covered by two cameras from opposite ends, the 20% overlap means each camera covers slightly past the midpoint. This costs nothing (it uses existing camera coverage) but guarantees no blind spot at the centre.

Mandatory Coverage Points: Bangladesh Bank Requirements

Camera Density Guidelines by Facility Type

These density guidelines are based on practical security standards. They are starting points — the actual design must be adapted to the specific floor plan.

Step-by-Step Planning Methodology

Step 1: Obtain a Floor Plan

Obtain a dimensioned floor plan of the building. If none exists, measure and sketch the floor plan yourself or engage a CAD technician. Accurate dimensions are essential for correct camera placement.

Step 2: Mark Security Objectives

On the floor plan, mark:

• Red zones (mandatory coverage): Every compliance-required point, every entry/exit, cash handling areas, restricted access zones
• Orange zones (recommended coverage): Corridors, common areas, car parks, loading areas
• Yellow zones (optional coverage): Open offices, general storage, non-sensitive areas

Step 3: Position Cameras to Cover Red Zones

Place a camera symbol at every red zone. Each mandatory point requires its own dedicated camera. Do not share a camera between two mandatory points if there is any risk that one point could be outside the frame.

Step 4: Position Cameras to Eliminate Blind Spots in Orange Zones

Working outward from red zones, position cameras to cover orange zone areas. Aim to eliminate all dead-end alcoves, stairwells, lifts, and side corridors in orange zones.

Step 5: Calculate Coverage Overlap

Verify that adjacent cameras overlap by at least 20% of their coverage zone width. If two cameras leave a gap, either reposition them or add a camera.

Step 6: Check IR Range for Night Coverage

For each outdoor and low-light camera, verify the IR range is sufficient to illuminate the full coverage zone at night.

Step 7: Count and Specify

Count the total cameras by type (indoor/outdoor, fixed/PTZ, standard/4K) and produce a camera schedule listing camera location, model, lens, and resolution.

Worked Example: 3-Floor Office Building in Dhaka

Building description:

• 3 floors above ground (Floors 1–3) + 1 basement car park
• Ground floor: Reception lobby (150 sqm), 4 meeting rooms, server room, 2 stairwells, 2 lifts
• Floors 2–3: Open-plan office (600 sqm each), 2 enclosed offices, 1 kitchen, 2 stairwells, 2 lifts
• Basement: 50-bay car park, 2 entry/exit ramps

Basement Car Park (50 bays)

• 2 vehicle entry cameras (at each ramp, capturing approaching vehicles for LPR): 2 cameras
• 2 vehicle exit cameras (at each ramp exit): 2 cameras
• General car park coverage — 1 wide-angle per 2 rows of bays: 8 cameras
• Basement total: 12 cameras

Ground Floor

• Main entrance door (exterior facing): 1 bullet camera (IP66, 4K for licence plate + face)
• Main entrance lobby (interior view): 1 dome camera (wide angle, IK10)
• Reception desk (teller-style close-up): 1 dome camera (4MP)
• Fire exit door 1 (rear): 1 dome camera
• Fire exit door 2 (side): 1 dome camera
• Server room entry: 1 dome camera (mandatory)
• Corridor connecting stairs/lifts: 2 dome cameras
• Lift lobby (cameras in each lift cab): 2 dome cameras (1 per lift cab)
• Stairwell 1 (landing view): 1 dome camera
• Stairwell 2 (landing view): 1 dome camera
• Ground floor total: 12 cameras

Floors 2 and 3 (repeated layout)

Per floor:

• Open-plan office (600 sqm ÷ 250 sqm/camera): 3 cameras
• 2 enclosed office corridors: 1 camera
• Kitchen/break area: 1 camera
• Stairwell landings: 2 cameras
• Lift lobby: 1 camera
• Per floor: 8 cameras × 2 floors = 16 cameras

Summary

Camera type breakdown:

• Indoor dome cameras (2MP, H.265): 30
• Indoor dome cameras (4MP, high-detail): 4 (reception, server room entry, manager office)
• Outdoor bullet cameras (4K, IP67): 2 (main entrance)
• Wide-angle dome cameras (4MP, car park): 8

Storage Calculation (30-day retention)

Mixed bitrate: approximately 2.0 Mbps average across all 40 cameras with H.265:

Storage = 2.0 × 0.0108 × 30 × 40 = 25.9 TB

NVR specification: 32-channel NVR (with capacity for 8 additional cameras) with 4 × 8TB surveillance-grade HDDs in RAID 5 = 24TB usable. Adequate for 30-day retention with margin.

For 90-day retention: 3 × RAID 5 arrays of 3 × 8TB = 72TB usable — meets the requirement comfortably with headroom.

Common Camera Placement Mistakes to Avoid

Mounting too high: Cameras mounted above 5 metres for indoor applications may capture top-of-head views only, making facial identification impossible. Ideal indoor mounting height is 2.5–3.5 metres.

Pointing into bright light: Cameras facing windows during daytime will be back-lit, rendering subjects as silhouettes. Mount cameras with the light source behind them, or specify wide dynamic range (WDR) cameras for back-lit locations.

Ignoring IR reflection: Cameras inside dome covers can suffer IR reflection at night. Test every camera in night mode before commissioning.

Covering maintenance-only areas with expensive cameras: Plant rooms, cable ducts, and utility areas accessed by maintenance staff only rarely need more than 720p cameras. Budget accordingly.

Forgetting lift interiors: Every lift interior needs a camera. This is frequently missed in camera counts and then requires difficult post-installation work inside lift cabs.

Key Takeaways

• Camera count is an output of the design process — it cannot be determined without a floor plan and security objective analysis
• Every mandatory coverage point requires a dedicated fixed camera — no exceptions for compliance-regulated facilities
• The 20% overlap rule eliminates blind spots between adjacent cameras
• Bangladesh Bank mandates specific coverage points for bank branches — document your compliance layout in a formal site map
• For a typical 3-floor office building, expect approximately 10–15 cameras per floor depending on size and layout complexity
• Common mistakes include mounting cameras too high, pointing into light sources, and forgetting lift interiors

Ready for a Professional Camera Count?

SSAL's design team creates detailed camera placement plans for buildings of any size, using field-of-view modelling software to verify coverage angles and identify blind spots before installation begins. Our free site surveys include a preliminary camera layout plan.

Contact SSAL for a free camera placement design:

• 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

Have a floor plan already? Send it to our design team at info@smartsafety.com.bd and we will provide a preliminary camera placement layout within 48 hours at no charge — giving you a professional specification to compare against any other vendor's quotation.