How do I calculate CCTV storage requirements?

Multiply: camera_bitrate (Mbps) × 3600 (seconds in an hour) × hours_per_day ÷ 8 (Mbps→MB) ÷ 1024 (MB→GB) to get GB per camera per day. Multiply by retention days and camera count for total GB. Divide by 1024 for TB. A typical 16-camera 1080p H.265 install recording 24/7 at 15 fps needs about 1.3 TB per day, so 30-day retention is roughly 40 TB.

Which codec uses less storage: H.264 or H.265?

H.265 (HEVC) uses approximately 50% less storage than H.264 at the same visual quality. H.265+ / Smart Stream (Hikvision / Dahua / Axis vendor variants) cut another 30-40% by adapting bitrate to scene activity. For new installs in 2026, default to H.265 or H.265+ if every camera in the system supports it. Mixed-codec installs are a maintenance burden — pick one and stick to it.

How big a hard drive do I need for 30 days of CCTV recording?

Depends on cameras × resolution × fps × codec. A 4-camera 1080p H.265+ home install at 15 fps with motion-only recording (~8 hours active per day) needs about 2-3 TB for 30 days. A 16-camera 4 MP H.265+ retail install at 25 fps recording continuously needs 12-18 TB for 30 days. Use the calculator above for your exact configuration.

Should I use RAID for CCTV storage?

For commercial installs: yes. RAID 5 (single-drive redundancy, n+1 drives) is the industry default — one drive can fail without data loss. RAID 6 (n+2 drives, double redundancy) is recommended for 8+ drive arrays where rebuild time on RAID 5 becomes risky. For residential / small office: a single surveillance-rated drive (WD Purple, Seagate SkyHawk) is usually sufficient if you accept the risk of footage loss on a single-drive failure.

What HDD type should I use for CCTV?

Use surveillance-rated drives: WD Purple, Seagate SkyHawk, Toshiba S300. These are designed for 24/7 write-heavy workloads with high vibration tolerance (multi-drive NVRs), AllFrame / ImagePerfect firmware for video streams, and 1M-hour MTBF ratings. Avoid desktop drives (WD Blue, Seagate Barracuda) — they drop frames under sustained write load and fail fast in surveillance use.

How does motion-only recording affect storage?

Motion-based recording typically cuts storage by 60–80% in indoor / private installs (very quiet at night) and by 30–50% in mixed environments. For public areas (retail, transit), motion is near-constant during business hours and the savings are minimal. Use the 'hours/day' slider in the calculator to model this — set it to your expected motion-active duration per day, not the wall-clock recording window.

CCTV Storage Calculator — HDD Size & RAID Sizing

Pick cameras, resolution, frame rate, codec and retention — get total HDD size and RAID 5 drive count for your NVR. Free, no signup.

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Number of cameras: 16

Resolution

Frame rate: 15 fps

Codec

Hours recorded per day: 24 h

Continuous = 24 h. Business hours = 8–12 h. Motion-only = 4–10 h depending on traffic.

Retention period: 30 days

Storage required

Total storage

14.8 TB

3.0 Mbps per camera at the chosen settings, 31.6 GB per camera per day across 16 cameras.

Recommended drives

3 × 16 TB (RAID 5)

Surveillance-rated drives only: WD Purple, Seagate SkyHawk, Toshiba S300. RAID 5 gives single-drive redundancy on commercial installs.

Related tools

Advanced storage calculator →

Mixed-camera groups, per-stream retention, PDF report

Bandwidth calculator →

Switch uplink + NVR throughput for the same camera config

PoE budget calculator →

Switch power for the same camera count

Plan the full system in one tool

Drop the cameras on a real map, get storage, PoE, bandwidth and BoM in one PDF. Free, no signup.