CCTV Recording Planning: Bitrate, Time and Capacity

Define what must be retained

The facility owner defines recorded cameras, schedules, required retention and event retrieval. Continuous and event-based recording differ. Confirm user and project requirements; this guide does not prescribe a legally required retention period.

Use visible assumptions

At a basic level, recorded data follows average data rate multiplied by duration. Use consistent bit, byte and time units when adding cameras. This is not the complete system requirement: reserve space, audio, metadata, storage configuration and genuinely usable capacity need separate consideration.

Bitrate depends on the scene

Axis discusses how video settings and bitrate-control strategies affect image quality and storage. A quiet scene's value does not automatically represent a busy period or nighttime. Reducing bitrate can change available detail, so capacity decisions should be assessed against the surveillance objective.

Validate after installation

Keep calculation assumptions, recording settings and capacity records. Once representative operation is available, check the oldest retained recording and playback or export functions. Revisit estimates when conditions change. A retention figure in a quotation needs a basis, not a uniform promise for every site.

Worked example: 16 cameras, 4 Mbps, 30 days

Assumptions: 16 cameras, an average of 4 Mbps per camera, recording 24 hours daily for 30 days. Video data = 16 × 4 × 1,000,000 ÷ 8 × 86,400 × 30 = 20,736,000,000,000 bytes, or 20.736 decimal TB. In the same units: TB = camera count × average Mbps × days × 0.0108.

This is hypothetical video data only. Audio, metadata, reserve space, redundancy and the difference between installed and usable storage are excluded. It is not a recommended disk size or a guarantee of 30-day retention.

What changes when bitrate changes?

For the same 16 cameras and 30 days, an average of 2 Mbps produces 10.368 TB; 6 Mbps produces 31.104 TB. Resolution or camera count alone is therefore insufficient for storage selection. Bring the required retention, recording settings, a justified bitrate and NVR configuration when discussing the system with GTI.