CCTV storage calculator: how many terabytes do you need?
Recorder storage is the part of a CCTV system that is most often under-sized. The calculation is simple once you know the bitrate of each camera, and it is worth doing before you order, because adding disks later can mean replacing the recorder.
The formula
- Per camera, per day: bitrate in Mbps × 10.8 = GB per day for 24-hour continuous recording. (1 Mbps is 1,000,000 bits per second; over 86,400 seconds that is 10.8 GB.)
- Whole system: GB per day × number of cameras × days of retention = total GB.
- Convert and add headroom: divide by 1,000 for TB, then add about 20% for growth, event clips and the space that formatting and RAID use.
Typical bitrates for planning
| Camera resolution | Typical bitrate with H.265 | Storage per camera per day (24 h) |
|---|---|---|
| 2 MP (1080p) | 1 to 2 Mbps | 11 to 22 GB |
| 4 MP | 2 to 4 Mbps | 22 to 43 GB |
| 5 MP | 3 to 5 Mbps | 32 to 54 GB |
| 8 MP (4K) | 4 to 8 Mbps | 43 to 86 GB |
These are planning ranges, not guarantees. The real bitrate depends on the codec (H.264 usually needs 1.5 to 2 times more than H.265), the frame rate, how much movement is in the scene and the smart-compression settings. After installation we check the actual bitrate and adjust.
Worked examples
| Site | Cameras and bitrate | Per day | 30 days | With 20% headroom |
|---|---|---|---|---|
| Villa | 8 cameras at 3 Mbps | 259 GB | 7.8 TB | about 9.3 TB, so choose 10 TB |
| Shop | 16 cameras at 3 Mbps | 518 GB | 15.6 TB | about 18.7 TB, so choose 20 TB |
| Warehouse | 32 cameras at 5 Mbps | 1,728 GB | 51.8 TB | about 62 TB, so choose 64 TB |
Check for yourself with the shop: 3 Mbps × 10.8 = 32.4 GB per camera per day; × 16 cameras = 518.4 GB per day; × 30 days = 15,552 GB, or 15.6 TB.
Ways to reduce the storage you need
- Use H.265 (or a smart-codec mode) instead of H.264.
- Record on motion or events in quiet areas. If a camera sees activity for 40% of the day, it needs roughly 40% of the continuous figure, plus pre-event recording.
- Lower the frame rate where fine motion does not matter, for example 12 to 15 frames per second for a storeroom, and keep 25 for entrances and tills.
- Match resolution to the job. A corridor does not need 8 MP.
- Keep important clips longer by exporting them, instead of lengthening retention for every camera.
Disks and RAID
- Use disks designed for surveillance (24/7 writing), not desktop disks.
- Disk sizes are sold in decimal terabytes, and a recorder shows about 7% less once formatted.
- RAID protects recordings when a disk fails but uses capacity: RAID 5 gives up one disk and RAID 6 gives up two. Count usable capacity, not the sum of the disks.
- Large systems benefit from a dedicated storage server or a second recorder as a backup, instead of one very large single box.
How long should you keep recordings?
Set the period from your risk and any rules that apply to your business, not from the disk size. Thirty days is a common target for shops and offices. Some sites keep less, and some keep more for specific areas such as cash rooms.
Frequently asked questions
How many TB do I need for 16 cameras?
At 3 Mbps per camera and 30 days of continuous recording you need about 15.6 TB before headroom, so a 20 TB recorder is a sensible choice. With motion-based recording it can be much less.
Does a higher resolution camera always need more storage?
Usually yes, but modern codecs and smart compression reduce the difference. Resolution should follow the job the camera has to do, not the other way round.
Can I add more disks to the recorder later?
Only up to the number of bays in the recorder, so it is better to choose a recorder with spare bays when the system is designed.
What happens when the disks are full?
Recorders normally overwrite the oldest recordings first. That is why the calculation matters: it decides how many days are really available.
Next step: tell us how many cameras you have and how long you want to keep recordings, and we will size the storage in your quotation. See also our Panasonic network video recorders and the guide How to choose a CCTV system.