CCTV storage is simple arithmetic once you know one number: the bitrate each camera records at. Storage needed equals bitrate, times the number of cameras, times the number of days. As a working figure, a camera recording continuously at 4 megabits per second uses about 43GB a day, so eight such cameras need roughly 10TB for 30 days, 21TB for 60 days and 31TB for 90 days. Higher resolution raises the bitrate; efficient compression and event-based recording lower it, often by half or more. The tables below cover the common cases, and the formula lets you work out your own.
What is the formula?
CALC. Storage per camera per day in GB = bitrate in Mbps x 86,400 seconds / 8 bits per byte / 1,000 = bitrate x 10.8.
- 2 Mbps: 2 x 10.8 = 21.6GB a day
- 4 Mbps: 4 x 10.8 = 43.2GB a day
- 8 Mbps: 8 x 10.8 = 86.4GB a day
Total storage = GB per camera per day x cameras x days. This assumes continuous recording, in decimal gigabytes.
What bitrate do cameras record at?
| Camera resolution | Typical bitrate with H.265 | Typical bitrate with H.264 |
|---|---|---|
| 2MP (1080p) | 1 to 2 Mbps | 2 to 4 Mbps |
| 4MP to 5MP | 2 to 4 Mbps | 4 to 8 Mbps |
| 8MP (4K) | 4 to 8 Mbps | 8 to 16 Mbps |
These are common ranges, not specifications. Actual bitrate depends on frame rate, how busy the scene is, lighting and the camera's settings. The reliable figure is the one shown in your camera's or recorder's configuration page; use that.
How much for 30, 60 and 90 days?
Continuous recording, in terabytes.
| Cameras | Bitrate each | Per day | 30 days | 60 days | 90 days |
|---|---|---|---|---|---|
| 4 | 2 Mbps | 86GB | 2.6TB | 5.2TB | 7.8TB |
| 4 | 4 Mbps | 173GB | 5.2TB | 10.4TB | 15.6TB |
| 4 | 8 Mbps | 346GB | 10.4TB | 20.7TB | 31.1TB |
| 8 | 2 Mbps | 173GB | 5.2TB | 10.4TB | 15.6TB |
| 8 | 4 Mbps | 346GB | 10.4TB | 20.7TB | 31.1TB |
| 8 | 8 Mbps | 691GB | 20.7TB | 41.5TB | 62.2TB |
| 16 | 2 Mbps | 346GB | 10.4TB | 20.7TB | 31.1TB |
| 16 | 4 Mbps | 691GB | 20.7TB | 41.5TB | 62.2TB |
| 16 | 8 Mbps | 1,382GB | 41.5TB | 82.9TB | 124.4TB |
CALC example, 8 cameras at 4 Mbps for 60 days: 43.2 x 8 x 60 = 20,736GB, about 20.7TB. Other rows follow the same formula.
How do you turn that into drives and bays?
- Add headroom. Allow 15 to 20 percent above the calculated figure for busier scenes and for the file system.
- Add redundancy. With single-drive redundancy, usable capacity is (number of drives - 1) x drive size. Whether to use redundancy for surveillance is a judgment: it protects footage from a drive failure at the cost of one drive's capacity.
- Choose surveillance-rated drives, designed for continuous writing.
- Leave a bay free if you expect to add cameras.
CALC. 8 cameras at 4 Mbps for 60 days needs 20.7TB. Plus 20 percent: 20.7 x 1.2 = 24.8TB. Four 12TB drives with single redundancy give (4 - 1) x 12 = 36TB usable, which covers it with room to grow. The same requirement for 90 days, 31.1 x 1.2 = 37.3TB, would need four 16TB drives, giving 48TB.
How can you need less storage?
| Method | Effect | Trade-off |
|---|---|---|
| H.265 instead of H.264 | Roughly halves bitrate for similar quality | Camera and recorder must both support it |
| Smart or adaptive encoding | Lowers bitrate when the scene is still | Varies by camera; test the image quality |
| Event-based recording | Records at full quality only when something relevant happens | Depends on reliable detection; a missed trigger means no footage |
| Lower frame rate | 15 frames per second instead of 25 or 30 cuts bitrate noticeably | Less smooth motion |
| Dual streams | Continuous low-resolution stream, high-resolution on events | More set-up |
| Different retention per camera | Keep entrances 90 days, corridors 30 | More to manage |
| Lower resolution where detail is not needed | Lower bitrate | Cannot be recovered later |
AI cameras make event-based recording more dependable, because they trigger on people and vehicles and not on every shadow. A common compromise is continuous recording at a modest bitrate with higher quality on events. See AI cameras vs traditional CCTV.
Do not size CCTV storage from the camera count. Size it from the bitrate, which you can read off the camera, and the retention period, which you have to decide.
How long should footage be kept?
Long enough for its purpose and no longer. Thirty days is a common choice for general premises security, since most incidents are noticed within that time; some industries, landlords, insurers or licensing conditions specify longer. In Singapore, footage of identifiable people is personal data, and the Personal Data Protection Act requires organisations not to keep personal data once it is no longer needed for a business or legal purpose. Check any requirements that apply to your sector, set a retention period in writing, and let the recorder delete automatically. This is general information, not legal advice; see office CCTV and PDPA.
What else affects the design?
- Network. Eight cameras at 4 Mbps is 32 Mbps of constant traffic to the recorder: trivial for a wired gigabit network, but worth keeping on its own segment.
- Recorder limits. A NAS or NVR is rated for a maximum number of cameras and total bitrate.
- Power. A UPS keeps recording through brief power cuts.
- A second copy of key footage. Export and store incident clips separately; retention deletion applies to them too.
For the recording platform itself, see Synology Surveillance Station with AI cameras and Synology NAS vs traditional NVR.
Buying in Singapore
Surveillance drives: Seagate SkyHawk, 1TB to 8TB, from S$158, and Seagate SkyHawk AI, 8TB to 20TB, from S$567.50. Recording NAS: the Synology DS925+ 4-bay (S$1,260), DS1825+ 8-bay (S$2,148) or, for larger systems, the RackStation RS2423+ 12-bay (S$4,002) (listed 12 Nov 2026; prices change; ask for a current quotation). Send us your camera count, bitrates and retention period and we will size the drives for you. To start, use Request for Quotation on the product page, call (65) 6978 3502, email Sales@sourceit.com.sg or use our contact page.
Frequently asked questions
How do I calculate CCTV storage? Multiply each camera's bitrate in Mbps by 10.8 to get gigabytes per day, then multiply by the number of cameras and the number of days of retention.
How much storage do 8 cameras need for 30 days? At 4 Mbps each with continuous recording, about 10.4TB. At 2 Mbps it is about 5.2TB, and at 8 Mbps about 20.7TB.
How much storage does a 4K CCTV camera use per day? At a typical 4 to 8 Mbps with H.265, a 4K camera uses roughly 43 to 86GB a day when recording continuously.
How can CCTV storage be reduced? Use H.265 and smart encoding, record at full quality only on events, lower the frame rate, and set shorter retention for less important cameras.
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