CCTV Hard Drive Storage Calculator

It depends on your camera count, resolution, frame rate, codec, scene activity and how long you need to retain footage. As a reference point, 4 cameras at 2MP/25fps H.264 with typical activity, recording continuously for 31 days, needs about 5.36TB. Enter your own setup above for an exact figure.

Industry-standard reference figures (checked 2026-08-08) put a 2MP/1080p stream at around 4 Mbps and a 4MP stream at around 8 Mbps, both at 25fps H.264 with typical scene motion - roughly doubling as resolution doubles. Busier scenes with more motion need a noticeably higher bitrate at the same resolution and compression settings.

H.265 (HEVC) typically needs only about 55% of the bitrate of H.264 for the same visual quality (checked 2026-08-08) - so switching from H.264 to H.265 on the same camera setup can cut your storage requirement by nearly half.

The ICO's guidance on video surveillance, including CCTV, explains that UK GDPR's storage limitation principle means footage should not be kept longer than necessary for its purpose. Around 30-31 days is commonly used as a starting point for general commercial security CCTV, but this isn't a fixed legal maximum or minimum - you should set and be able to justify your own retention period based on your specific purpose.

If you enter a retention period well beyond the commonly used ~31-day benchmark (over 90 days, for example) without an obvious reason, the Assessment module flags it as worth double-checking against the UK GDPR storage limitation principle - not because longer retention is banned, but because it should be a documented, purpose-led decision rather than a default setting left unreviewed.

Continuous recording writes footage to storage 24/7 regardless of activity. Motion-triggered recording only writes footage when the camera detects movement, which can cut storage needs dramatically - this calculator models moderate motion-triggered activity at roughly 30% of the day and low activity at roughly 15%, though actual figures depend heavily on your camera's motion sensitivity settings and how busy the scene genuinely is.

Even if a camera only records to storage when it detects motion, most systems still need to support the camera's full streaming bitrate on the network for live viewing at any time. This calculator's combined-bitrate figure reflects the full streaming bitrate; only the daily/total storage figures apply the recording-mode reduction.

Once your total exceeds the largest commonly available single drive (around 24TB as of 2026-08-08), the calculator recommends a multi-drive or RAID array sized to your total capacity, rather than suggesting a single drive that doesn't exist at that size.

Yes, if you use a redundant RAID level (such as RAID 5 or RAID 6) for protection against drive failure, some of your raw drive capacity is used for parity data rather than footage - this calculator states the raw capacity needed and does not calculate RAID overhead, which varies by RAID level and number of drives.

Yes, meaningfully. A camera pointed at a busy road or a retail floor has far more motion between frames than one covering a quiet corridor, and modern compression (H.264/H.265) works by encoding the differences between frames - more motion means more data per frame, even at the same resolution and frame rate settings.

25fps is the standard UK/European frame rate (matching the PAL broadcast standard many CCTV systems still reference), while 30fps is more common in US/NTSC-influenced equipment. Either is normally smooth enough for security footage; higher frame rates increase both bitrate and storage needs roughly proportionally, with limited practical benefit for most static security scenes beyond about 15-25fps.

No - unlike the manufacturer calculators from Seagate, Western Digital and SanDisk that dominate this search, this tool is vendor-neutral. It estimates the storage capacity you need in TB; which brand or model of drive you then buy to reach that capacity is entirely up to you.

No. The ICO retention benchmark is cited for storage-planning purposes only. This calculator does not provide legal advice on UK GDPR compliance, camera positioning, signage, or your obligations under the Surveillance Camera Code of Practice - consult the ICO's guidance directly or a data protection professional for those questions.