How much storage a video archive needs: how to calculate for cameras
The recorder disk fills up faster than expected, or you bought twice what you need. The size of the archive is easy to calculate in advance.
The formula
Per day for one camera the size is the bitrate in megabits per second divided by 8 (megabytes per second) times 86,400 seconds. Then multiply by the number of cameras and retention days.
Where to get the bitrate
Look in the camera or recorder settings. It depends on resolution, frames per second, the codec (H.265 is usually much more economical than H.264) and scene complexity: a yard with trees in the wind is "heavier" than an empty corridor.
Motion recording versus continuous
With motion-only recording the size depends on how long something happens in frame. For a building entrance that can be a quarter of the day, for a quiet warehouse far less. For the calculation take a percentage with headroom.
Headroom and redundancy
- Add 15-25 % headroom: scenes change and cameras get added.
- If you use RAID, part of the space goes to redundancy.
- Surveillance disks are built for continuous recording, ordinary ones can wear out quickly.
- Disk makers count in decimal terabytes, so the system shows less.
How many days to keep
This is the owner's or the board's decision, together with legal requirements for keeping recordings and protecting personal data. Check them with a lawyer.
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