Most CCTV systems need a few terabytes (TB) for a month of footage. Eight 4MP cameras recording around the clock with H.265 compression need about 6.1 TB for 30 days, which fits an 8 TB surveillance hard drive with room to spare.
Your exact figure depends on your cameras and settings. Below are typical figures for 4 to 32 cameras, what changes them, and how to work out your own with our free CCTV Storage Calculator.
A quick rule of thumb
Allow about 0.8 TB a month for each 4MP camera recording 24 hours a day with H.265 at 15 fps. Add 10% headroom, then round up to the next drive size.
Typical CCTV storage for 30 days
These general figures are for 4MP cameras at 15 fps and Standard quality, recording continuously.
| Cameras | H.265 compression | H.264 compression |
|---|---|---|
| 4 | 3.1 TB (4 TB drive) | 4.9 TB (6 TB drive) |
| 8 | 6.1 TB (8 TB drive) | 9.9 TB (12 TB drive) |
| 16 | 12.3 TB (14 TB drive) | 19.8 TB (24 TB drive) |
| 32 | 24.5 TB (several drives) | 39.6 TB (several drives) |
Drive sizes include 10% headroom. Thirty-two cameras need more than a 24 TB drive, so split the storage across several drives: about 27 TB with H.265 or 43.5 TB with H.264, including headroom. These are the general estimates our calculator uses for cameras from any brand; your brand, scene and settings will change them.
for 30 days of recording, 24 hours a day
storage at the same settings
than continuous, if cameras record 30% of the time
What changes how much storage you need
Resolution
More pixels mean more data. At 15 fps with H.265, a camera needs about 0.5 TB a month at 2MP, 0.8 TB at 4MP and 1.2 TB at 8MP (4K).
Compression
H.265 needs about 38% less space than H.264 for the same settings. Smart codecs, which many brands offer, can save more, depending on movement in the scene.
Frame rate
Recording at 25 fps needs about 31% more space than 15 fps, and 6 fps about 44% less. Many systems record at 12 to 15 fps to balance smooth video and storage.
Image quality
Higher quality settings keep more detail but need about 72% more space than Standard. Lower quality needs about 54% less.
Recording mode
Motion only recording skips quiet periods. If cameras record about 30% of the time, eight 4MP cameras need about 1.8 TB for 30 days instead of 6.1 TB.
Retention period
Storage grows with the days you keep. Eight 4MP cameras need about 2.9 TB for 14 days, 6.1 TB for 30 days and 18.4 TB for 90 days.
For help choosing a resolution, read our guide to camera resolution: 2MP vs 4MP vs 8MP.
Use our CCTV Storage Calculator
The brand of CCTV you have, the settings and recording hours will change the figures which will provide the information you need to pick the right CCTV storage size. Our free CCTV Storage Calculator covers Ajax, Avigilon, Dahua, Hanwha, Hikvision and Pelco cameras, with general figures for other brands, for IP and analogue systems. Add a group for each type of camera and it suggests the drive size to fit.
Choosing the right hard drive
Use a surveillance-rated hard drive, designed to record around the clock. Leave about 10% headroom, as our calculator does, and round up to the next drive size. Before you buy, check:
- how many drive bays your recorder has, and the largest drive it supports
- whether it uses RAID or a spare drive for resilience, which reduces usable space
- whether you might add cameras later, as each one adds storage
Recording on site or in the cloud? Our guide to cloud vs local CCTV storage compares the options.
How long should you keep CCTV footage?
UK data protection law sets no fixed retention period for CCTV. The ICO says your purpose should decide how long you keep footage, so choose the shortest period that does the job and record why. Around a month is a common starting point, not a legal requirement. Read the ICO’s guidance on surveillance and data protection, or use our ICO Compliance Checker for registration guidance.
Planning a CCTV system?
Book a free survey and we’ll specify the cameras, recorder and storage for your premises, anywhere in Northern Ireland. You can also read about our CCTV installation service.
Advanced Overwatch is SSAIB certificated (NIRE127) for CCTV systems.