CCTV Storage Calculator
How many terabytes of HDD do you need for N cameras, a given bitrate and retention period?
How to use this tool
Enter the number of cameras, the average bitrate per camera in Mbps (check the camera web UI, not the datasheet maximum), recording hours per day and the days you must keep footage. Motion-only recording is modelled with a motion percentage. The result includes a 10% safety margin because file system overhead and bitrate spikes are real.
Worked example
8 cameras at 4 Mbps recording 24 h for 30 days = 8 × 4 Mbps × 86,400 s × 30 ÷ 8 ÷ 1e12 ≈ 10.4 TB raw, about 11.4 TB with a 10% margin, so plan 12 TB usable (before RAID).
Frequently asked questions
How much storage do I need for 8 cameras?
At 4 Mbps each, recording 24/7 for 30 days, about 11–12 TB. At 2 Mbps with H.265 it is roughly half. Use the calculator with your real bitrates.
Does H.265 really save space?
Typically 30–50% versus H.264 at similar quality, but the saving depends on the camera encoder and scene. Measure your own bitrate.
Should I use surveillance-rated drives?
Yes. Surveillance drives are designed for constant sequential writes and many simultaneous streams, which desktop drives handle poorly.