How to size CCTV storage

The formula

Storage (TB) = cameras × bitrate (Mbps) × 3600 × hours per day × days ÷ 8,000,000, plus headroom.

A 4-camera 1080p H.265 system at 2 Mbps recording 24 × 7 for 30 days needs about 2.6 TB before headroom.

What changes the answer

• Codec — H.265 roughly halves H.264 bitrate at the same quality.
• Motion-based recording — can cut storage by 40–70% in quiet areas, but a busy shop floor records almost continuously.
• Resolution and frame rate — 4 MP at 25 fps needs far more than 2 MP at 15 fps.
• Headroom — recorders need free space for indexes and event clips; keep 20% spare.

Drives

Use surveillance-rated drives (designed for continuous writes). The calculator suggests the nearest common capacity; buy the next size up if you expect to add cameras.

Use the storage calculator to get a number for your site.