CCTV Storage Calculator
Estimate the NVR disk space and network bandwidth a camera system needs. Change any value and the numbers update instantly.
Your system
Storage required
18.8 TB
for 16 cameras over 30 days
Roughly 1× 20 TB drive before any RAID redundancy.
Network bandwidth
52.8 Mbps
Total sustained throughput from cameras to the recorder.
Per camera
35.6 GB/day
At 3.3 Mbps per stream.
These are estimates based on typical variable-bitrate figures. Real usage moves with scene complexity — a car park at night records far less than a busy retail floor. If your cameras report their actual bitrate, enter it in the override field for an exact answer.
How CCTV storage is calculated
The formula
Storage comes from bitrate and time. One camera streaming at 1 Mbps produces about 0.45 GB every hour, so the calculation is: bitrate (Mbps) × 0.45 × hours per day × days × cameras.
Why H.265 halves your disk bill
H.265 (HEVC) encodes the same picture in roughly 45–55% of the bitrate H.264 needs. On a 30-day retention system that is the difference between 20 TB and 11 TB. Nearly every camera made since about 2018 supports it, and it is usually a single setting in the encoder menu — the most cost-effective change available on most installs.
Frame rate matters less than people expect
Doubling from 15 to 30 fps does not double storage. Video compression predicts each frame from the last, and more frequent frames are more similar, so the real increase is nearer 70%. For most identification work 12–15 fps is plenty.
Motion recording is not a guarantee
Motion-triggered recording only saves space if the scene is genuinely quiet. A camera facing a road with moving trees can trigger almost constantly and save nothing. Size the disks for the worst realistic case, not the best.
Leave room for RAID
The figure above is usable capacity. RAID 5 costs one drive of the array, RAID 6 costs two, and RAID 1 halves it. Surveillance-rated drives are also worth the premium — they are built for continuous sequential writes, which desktop drives are not.