CCTV Storage Calculation: Stop Losing Footage

Something goes missing from the store room. A dispute comes up at the gate. Someone asks for the footage from ten days ago, and the security team discovers the recorder only keeps five days. The older recordings were overwritten automatically, and the one clip that mattered is gone.

This happens in offices, factories, warehouses, schools and housing societies more often than most people realise. The cameras were working and recording. The problem was storage: the recorder was never sized for the number of cameras, the resolution and the number of days the organisation actually needs.

The fix is not complicated. With a simple CCTV storage calculation, the right recording settings and a bit of monitoring, you can make sure footage is there when you need it. Here is how.

Why CCTV Footage Disappears Early

Storage was sized for the old setup

Cameras get added over time, or old analog cameras are replaced with higher-resolution IP cameras. Each change increases the data being recorded, but the hard disks in the NVR or DVR stay the same. The recorder quietly overwrites older footage sooner.

Continuous recording at maximum quality

Many systems are installed with every camera recording 24 hours a day at the highest resolution and frame rate. That fills disks quickly, even for cameras watching an empty corridor at night.

Failed disks nobody noticed

When a hard disk fails in a recorder without redundancy, the system may keep running on the remaining disks with less space, or stop recording on some channels. If nobody checks the recorder's health alerts, this can go unnoticed for weeks.

No agreed retention period

Often nobody has decided how many days of footage the organisation needs. Without that number, storage is simply whatever came in the box.

How to Do a CCTV Storage Calculation

The key input is the bitrate of each camera stream, measured in megabits per second (Mbps). You can see this in the camera or NVR settings. Resolution, frame rate, compression and scene activity all affect it.

Use this simple formula for continuous recording:

Storage per camera per day (GB) = Bitrate (Mbps) x 86,400 seconds / 8 / 1,000

Dividing by 8 converts bits to bytes, and dividing by 1,000 converts megabytes to gigabytes.

Worked example

• Camera bitrate: 4 Mbps (an example value; check your own settings).
• Per camera per day: 4 x 86,400 / 8 / 1,000 = 43.2 GB.
• For 16 cameras: 43.2 x 16 = about 691 GB per day.
• For 30 days: 691 x 30 = about 20.7 TB.

Then add headroom. Keep 10 to 20 percent extra so the system is not running at the limit, and plan for any cameras you expect to add in the next couple of years. If you use motion-based recording, actual usage will be lower, but size for the busiest cameras, not the quietest.

The Fix: 6 Steps to Reliable CCTV Storage

1. Decide your retention period. Agree with management, security and, where relevant, your legal or compliance team how many days of footage you need. Check whether any client contract, insurer or sector regulator sets a minimum for your site.
2. Tune recording settings per camera. Not every camera needs the same quality. Entrances, cash counters and loading bays may need higher resolution. Corridors and parking areas can often use a lower frame rate or motion-based recording.
3. Use efficient compression. Newer codecs such as H.265 can reduce bitrate compared with H.264 at similar visual quality, which directly cuts storage needs. Check that your cameras and recorder both support it.
4. Calculate and size storage properly. Use the formula above with your real bitrates, add headroom, and choose surveillance-rated hard disks designed for continuous writing.
5. Add redundancy. For important sites, use a recorder or storage that supports RAID, so a single disk failure does not wipe out recordings. For critical footage, export or back up important clips to separate storage.
6. Monitor health and test retrieval. Turn on disk health and recording-failure alerts and send them to someone who will act. Once a month, try to retrieve footage from the oldest day you should have. If it is missing, you know before an incident does.

Where Should Recordings Live?

For a single office or small site, a standalone NVR with the right number of disk bays is usually enough. Check how many disks it supports and the maximum capacity per disk before you buy, so you have room to grow.

For larger campuses, factories or organisations with many branches, a central video management system with dedicated storage can make more sense. It lets the security team search footage from all sites in one place, apply the same retention rules everywhere and manage disk health centrally. The trade-off is network bandwidth: each camera stream has to reach the central storage, so plan your LAN and WAN links along with the storage.

Whatever you choose, document it: which cameras record where, at what settings, for how many days, and who is responsible for checking. This one page saves hours when an incident happens or when the person who installed the system is no longer around.

Common Mistakes to Avoid

• Counting only cameras, not bitrate. Two sites with 16 cameras each can need very different storage depending on resolution and settings.
• Using desktop hard disks. Disks not designed for 24x7 surveillance workloads tend to fail sooner.
• Keeping the recorder on an open network. An NVR with default passwords or exposed to the internet is a security risk. Change default credentials, update firmware and place cameras on a separate network segment.
• Forgetting power. Sudden power cuts can corrupt recordings and disks. Put the recorder and core network switches on a UPS.

If you are still choosing camera technology, our comparison of IP CCTV vs analog CCTV explains how each option affects quality, cabling and storage.

Frequently Asked Questions

How many days of CCTV footage should we keep?

There is no single answer for every site. Decide based on how quickly incidents are usually reported, your security needs, and any requirement from clients, insurers or regulators that applies to you. Many organisations choose a period of a few weeks, but set yours deliberately.

Does motion recording save much storage?

It can, especially for cameras covering areas that are empty for long periods. Test it carefully so important events are not missed, and keep continuous recording for critical areas.

Can we store CCTV footage in the cloud?

Yes, cloud or hybrid options exist, but they need enough upload bandwidth and a clear view of ongoing costs. Many sites keep local recording and send only important clips or selected cameras to the cloud.

How do we know our storage is enough?

Check the oldest recording available on each channel and compare it with your agreed retention period. Repeat this check monthly and after adding cameras.

How Affix Center Helps

Affix Center designs, installs and maintains CCTV and surveillance systems for offices, factories, warehouses and public sector sites. We audit your current setup, calculate the right storage, tune camera settings and add monitoring so recordings are always available. Our IT operations team can keep an eye on recorder health, while our cybersecurity specialists help secure cameras and recorders on your network. You can see the sectors we work with on our industries page.

Do not wait for an incident to find out your footage is missing. Contact Affix Center for a CCTV storage review.