One of the most common CCTV surprises is finding out, after an incident, that the recorder only kept a few days of footage. Choosing the right hard drive size up front avoids this. This guide explains how CCTV storage works and how to estimate what you need.
How CCTV storage works
Your recorder (NVR or DVR) saves footage from every camera to its hard drive. When the drive is full, it automatically records over the oldest footage. So the size of the hard drive decides how many days back you can go when you need to find a recording.
What affects how much storage you need
- Number of cameras: each camera adds its own stream of video
- Resolution: higher resolution cameras produce more data
- Bitrate: the amount of data the camera sends each second, which depends on resolution, frame rate, and compression
- Compression: H.265 uses much less storage than older H.264 for similar quality
- Recording mode: continuous recording uses the most storage; motion-only recording uses much less
- Activity: busy scenes with lots of movement use more data than quiet scenes
A simple way to estimate storage
A useful rule of thumb: 1 Mbps of bitrate uses about 10.8 GB per day of continuous recording.
For example, four cameras each recording at around 2 Mbps use about 8 Mbps in total. That is roughly 86 GB per day, so:
- a 1TB drive keeps around 11 days of footage
- a 2TB drive keeps around 23 days
- a 4TB drive keeps around 46 days
These are estimates. Actual bitrates vary with resolution, compression, and settings, so check the bitrate shown in your recorder's settings for a more accurate figure.
How many days of footage should you keep?
For homes, two to four weeks is usually enough. For shops and offices, keeping at least a month is wise, because theft or disputes are often noticed days or weeks later. Some businesses keep footage longer for their own policies.
Use a surveillance hard drive
Surveillance hard drives are designed to write video 24 hours a day, every day. Ordinary desktop drives are built for lighter use and can fail sooner in a recorder. Always check the recorder's maximum supported drive size and the number of drive bays before buying.
Ways to make storage last longer
- Use H.265 or H.265+ compression if your cameras and recorder support it
- Record on motion for quiet areas, and continuously for key areas such as entrances and counters
- Use a lower frame rate where smooth motion is not needed
- Add a second hard drive if your recorder has a spare bay
- Protect the recorder with a UPS, because sudden power cuts can damage hard drives
Frequently asked questions
Can I use a normal computer hard drive in a CCTV recorder?
It may work, but it is not recommended. Surveillance hard drives are built to record video continuously, day and night, and usually last longer in a recorder than ordinary desktop drives.
What happens when the CCTV hard drive is full?
The recorder automatically records over the oldest footage, so recording never stops. That is why the drive size decides how many days back you can search.
Can I back up important footage?
Yes. You can export clips from the recorder or the mobile app to a USB drive or your phone. Save important clips straight away, before they are overwritten.
Get the right storage for your system
We size the storage for every system we install, based on your cameras and how long you need to keep footage. See our NVR systems and accessories, read NVR vs DVR, or ask about our CCTV installation service.