How much storage does a CCTV recording system need?
Megapixels alone cannot size a disk. Capacity depends mainly on actual bitrate, recording hours, retention and the number of streams.
A common CCTV sizing mistake is choosing storage from camera resolution alone. Two 4K cameras can produce very different data volumes because of bitrate, frame rate, codec and scene complexity.
A useful estimate needs the bitrate of each stream, camera count, recording hours per day, retention days and a reserve for variation and recorder operation.
Convert bitrate into capacity
A constant 8 Mb/s stream writes about 1 MB every second, or roughly 86.4 GB per day. Five such cameras recording continuously produce about 432 GB per day before overhead and reserve.
- Add the main streams for every camera.
- Multiply by actual recording time.
- Multiply by the required retention period.
- Add reserve for variable bitrate and system operation.
Continuous or event recording
Event recording can reduce consumption substantially, but the result depends on scene activity and detection quality. Do not assume a fixed saving without measuring the location. Critical areas often use continuous recording with event markers.
Disks, RAID and real retention
Use drives designed for continuous recording and check recorder limits: bay count, maximum disk size and supported RAID. RAID improves disk-failure tolerance but consumes usable capacity and is not a backup of important footage.
- Calculate usable capacity after RAID.
- Account for automatic overwrite of the oldest footage.
- Compare the estimate with actual consumption after deployment.
- Test playback and export, not just disk health indicators.
Inputs for a retention calculation
- Camera count and main-stream bitrate.
- Recording hours and continuous/event mode.
- Required retention days.
- Usable capacity after RAID plus a safety reserve.
Put it into practice
Calculate CCTV storage
Enter camera count, bitrate, recording time and retention to size capacity and compare configuration variants.
Calculate CCTV storageFrequently asked questions
How many days fit on an 8 TB disk?
It cannot be answered without bitrate and camera count. At a combined 40 Mb/s, recording uses about 432 GB per day, so nominal 8 TB does not equal a full 19 days after real capacity and reserve.
Does H.265 always halve storage?
No. Savings depend on the scene, quality settings, frame rate and device implementation. Use the configured or measured bitrate of the actual camera.
Is RAID a recording backup?
No. RAID can tolerate a disk failure but does not protect against deletion, recorder failure, theft or operator error.