How Much Storage Do I Need for a 16-Camera CCTV System

Sizing storage for a multi-camera CCTV installation comes down to one formula with five inputs, and understanding which input actually drives the total most matters more than memorizing the formula itself, since it’s the one most people underestimate when specifying a system.

The formula

Total storage needed is: (Bitrate × 3600 seconds × Hours Recorded per Day × Days of Retention × Number of Cameras) ÷ 8 ÷ 1024³, converting from bits to bytes and then into gigabytes. An 8-camera system at 2048 Kbps per camera, recording 24 hours a day with a 30-day retention requirement, needs about 4.83 TB. Scale that up to a 16-camera system at a higher 4096 Kbps per camera, recording only 12 hours a day but with a longer 60-day retention window, and the total jumps to about 19.31 TB — roughly four times the storage, from cameras doubling, bitrate doubling, and retention doubling, even though recording hours per day actually halved.

Why bitrate matters more than resolution

Camera resolution gets most of the attention when people spec out a CCTV system, but it’s bitrate — the actual rate of data the camera and its compression encoder produce, measured in Kbps or Mbps — that directly drives storage consumption, not resolution as a standalone number. Two cameras at the identical resolution can have meaningfully different bitrates depending on compression codec (H.265 is roughly 30-50% more storage-efficient than the older H.264 for comparable visual quality), scene complexity (a busy scene with lots of motion produces a higher real bitrate than a static scene, for encoders using variable bitrate compression), and the specific quality setting chosen for that camera’s encoder configuration.

This is exactly why spec sheets quoting only camera resolution (“4K cameras”) without also specifying the actual expected bitrate at that resolution and codec don’t give enough information to size storage accurately — two “4K” systems from different manufacturers or with different compression settings can have substantially different real-world storage requirements despite matching resolution numbers.

The retention-versus-cost tradeoff

Retention period — how many days of footage the system keeps before overwriting the oldest recordings — is usually the single largest lever on total storage need, since it multiplies directly against every other factor in the formula. Many jurisdictions and industries have specific minimum retention requirements (commonly 30-90 days for general commercial CCTV, sometimes longer for regulated industries like banking or healthcare) — checking the actual applicable requirement before sizing storage is worth doing early, since retroactively discovering a system needs to retain footage twice as long as originally planned means a full storage re-sizing, not a minor adjustment.

Continuous vs motion-triggered recording

The formula above assumes continuous recording for the specified hours per day, but many real systems use motion-triggered or scheduled recording instead, only actually writing footage when meaningful activity is detected (or during specific hours) rather than genuinely continuously. This can reduce real storage consumption substantially compared to the continuous-recording formula — sometimes by 50% or more for a low-traffic area — but it comes with a real tradeoff: motion-triggered recording risks missing the first fraction of a second before motion detection actually triggers, and depends on the detection sensitivity being correctly tuned, neither of which continuous recording has to worry about. Many serious installations use continuous recording specifically for this reliability reason, treating the higher storage cost as a worthwhile tradeoff against the risk of a missed event.

Sizing a real system

The CCTV Storage Calculator on this site applies this exact formula directly — enter camera count, per-camera bitrate, recording hours per day and retention period to get a direct storage total in both GB and TB. For working backward from a fixed available storage budget to find the maximum retention period it supports, the NVR Retention Days Calculator inverts the same calculation. Since a larger camera count also drives real network bandwidth requirements alongside storage, the Network Bandwidth Calculator covers that related sizing question, and the PoE Power Budget Calculator covers the physical power delivery side of a multi-camera installation.