How much storage cameras need
A network video recorder (NVR) writes each camera’s video stream continuously or when motion is detected. The storage needed is simply the data rate multiplied by the recording time:
Storage = cameras × bitrate × hours per day × share recorded × retention days
With bitrate in megabits per second, divide by 8 to get megabytes per second. One megabit per second is 10.8 GB per day of continuous recording.
Typical bitrates
| Camera | Codec | Typical bitrate | Per day, 24/7 |
|---|---|---|---|
| 1080p (2 MP) | H.264 | 4 Mbit/s | 43.2 GB |
| 1080p (2 MP) | H.265 | 2 Mbit/s | 21.6 GB |
| 4 MP | H.265 | 4 Mbit/s | 43.2 GB |
| 4K (8 MP) | H.265 | 8 Mbit/s | 86.4 GB |
Real bitrates depend on frame rate, scene complexity, night noise and quality settings. Check the stream statistics in your NVR for the best estimate.
Example
Four 1080p H.264 cameras at 4 Mbit/s recording 24/7 for 30 days write 172.8 GB per day and need 5.2 TB. With 15% headroom for file system overhead and bitrate peaks, a 6 TB drive fits.
Ways to save space
- H.265 or H.265+ roughly halves the size compared with H.264.
- Motion recording often cuts storage by 50 to 80%, but you lose context around events.
- Lower frame rates: 15 frames per second is enough for most security uses.
- Sub-streams: some systems record a low-resolution stream continuously and the main stream only on events.
Choosing drives
- Use surveillance-rated drives (such as WD Purple or Seagate SkyHawk), designed for continuous writing.
- For several drives, RAID 1, 5 or 6 protects recordings against a single drive failure, at the cost of capacity.
- The NVR overwrites the oldest footage when the disk is full, so the retention period is set by capacity.
Bandwidth
Total bandwidth equals the sum of the camera bitrates. Four 4 Mbit/s cameras use 16 Mbit/s on the network, well within a gigabit switch, but remote viewing over a slow upload connection may need lower-quality sub-streams. Check local laws before recording public areas or neighbors’ property.