The short answer
Storage needs depend on resolution, the number of cameras, frame rate and whether you record continuously or on motion — and footage is typically kept on a rolling basis until the drive fills and overwrites the oldest, often giving days to a few weeks. Higher resolution (4K versus 1080p), more cameras, higher frame rates and 24/7 recording all consume more space, so a multi-camera 4K system needs a far larger hard drive than a single 1080p camera. Most systems overwrite the oldest footage automatically once the drive is full, so capacity sets how many days you keep. Under the ICO's domestic-CCTV guidance there is no fixed legal period, but you should keep footage no longer than necessary for its purpose. Sizing the drive for your desired retention is the key decision.
Storage is one of the most misunderstood parts of CCTV — the right amount depends on several factors, and retention is a rolling window, not a fixed archive. The sections below explain how to size it and how long to keep footage.
What drives storage need
- Resolution4K uses far more than 1080p
- CamerasMore cameras = more storage
- Recording modeContinuous uses more than motion
- Frame rateHigher fps uses more
- RetentionRolling — overwrites oldest when full
What actually decides how much storage you need
There is no single answer, because storage need is driven by several factors multiplied together. The biggest is resolution: 4K footage has roughly four times the pixels of 1080p, so it uses dramatically more space. Next is the number of cameras — each camera adds its own stream, so a four-camera system needs about four times the storage of one camera, all else equal. Recording mode matters too: continuous (24/7) recording fills a drive far faster than motion-only recording, which captures only events. Frame rate (frames per second) and the compression the system uses (modern codecs like H.265 are more efficient than older ones) also affect file sizes.
Because of this, the honest answer is to size the drive to the system: more cameras, higher resolution, higher frame rate and continuous recording all push the capacity up. Many recorders include a storage calculator, and manufacturers publish estimates, so you can work out roughly how many days a given drive holds for your exact setup before you buy.
How long footage is kept, and the rules
Most CCTV stores footage on a rolling basis. The recorder writes to the hard drive until it is full, then overwrites the oldest footage first, so you always have the most recent period available. The number of days you keep is therefore set by the drive capacity relative to how fast you record — a bigger drive, or a more efficient/motion-only setup, keeps more days. A typical home system might hold anywhere from a few days to a few weeks before it loops, depending entirely on the factors above. If you need a specific event preserved, you usually export or back it up before it gets overwritten.
On how long you should keep it, the ICO's domestic-CCTV guidance is clear that there is no fixed legal retention period for home CCTV, but you should keep footage no longer than necessary for the purpose you collected it for, and delete it when it is no longer needed. The table gives a feel for what pushes storage up or down.
| Factor | Uses less storage | Uses more storage |
|---|---|---|
| Resolution | 1080p | 4K |
| Cameras | One | Several |
| Recording mode | Motion-only | Continuous 24/7 |
| Frame rate | Lower fps | Higher fps |
| Compression | H.265 (efficient) | Older codecs |
Indicative factors for guidance. Sources: manufacturer specifications, ICO.
Choosing capacity and keeping footage safe
To choose capacity, work backwards from how many days you want to keep. Decide a target retention (say a week or two), enter your resolution, camera count, frame rate and recording mode into the recorder's storage calculator, and pick a hard drive that comfortably exceeds the result so you are not constantly on the edge of overwriting. It is worth fitting a drive designed for surveillance (these are built for continuous writing), and remembering that switching some cameras to motion-only or using efficient compression can stretch the same drive much further. If you ever need longer history than the drive holds, export important clips or add cloud/off-site backup.
Keeping footage safe and compliant matters as much as having enough of it. Local storage is lost if the recorder is stolen or the drive fails, so an off-site backup of key clips guards against that. Secure the system with strong passwords and up-to-date firmware, especially if it is reachable remotely, and under the ICO's guidance keep footage only as long as necessary, store it securely against unauthorised access, and be able to provide footage of a person if they make a valid request. Sizing the drive sensibly, choosing the right recording mode, and managing retention deliberately gives you enough useful history without keeping more than you should — which is exactly what the rules ask.
Frequently asked questions
How many days of footage can a CCTV hard drive hold?
It varies widely with resolution, camera count, frame rate and whether recording is continuous or motion-only. A home system might hold from a few days to a few weeks before it loops and overwrites the oldest footage. The recorder's storage calculator gives an accurate figure for your specific setup.
How long am I legally allowed to keep home CCTV footage?
The ICO's domestic-CCTV guidance sets no fixed legal retention period for home CCTV, but advises keeping footage no longer than necessary for the purpose you collected it for, and deleting it when no longer needed. Keep it secure while you hold it and be able to respond to valid requests about it.
Does motion-only recording save storage compared with continuous?
Yes, considerably. Motion-only recording captures clips when something is detected rather than filling the drive around the clock, so it generally keeps more days on the same hard drive. The trade-off is that you may miss context between events, and motion-triggered systems can briefly miss the very start of an incident.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific property and system. They are guidance, not a quotation.