How much storage does a CCTV system need?
Cameras, resolution, recording days and compression: how to estimate the hard disk size for your NVR.
Updated 26 Oct 2026
The hard disk in your NVR decides how many days of footage you keep. Too small and you lose footage before anyone notices an incident; too big and you pay for disks you do not need.
The four things that decide the size
- Number of cameras.
- Resolution. 4 MP and 8 MP (4K) cameras produce much more data than 2 MP cameras.
- Recording days. Many businesses keep 30 days; some sectors are asked to keep longer.
- Compression. H.265 needs roughly half the space of H.264 for similar quality.
Motion-only recording uses far less space than recording all day, but it can miss events, so most offices record continuously at a lower frame rate.
A rough rule
A 2 MP camera recording continuously with H.265 uses roughly 10 to 25 GB a day (a 1 to 2 Mbps stream), depending on the scene and frame rate. A busy scene with lots of movement uses more than an empty corridor. Multiply by cameras and days, then add 20 percent headroom.
The CCTV storage calculator on this site does this sum for your camera count and suggests a disk size.
Do not forget
- Use surveillance-grade drives made for recording around the clock.
- Check how many drive bays the NVR has, and whether it supports RAID so one failed disk does not lose everything.
- Ask whether the quote includes cabling, installation and mobile app setup.