Security Camera Storage Calculator: Plan Recording and Retention

1. Define what needs to remain available

How long after an incident might someone need footage? Set a retention target for each camera group and identify events that need separate preservation. The recorder's maximum available history should not define the business policy.

Decide whether the requirement is continuous video or event clips, and whether the same image quality must remain available for the entire period. Record who approves these choices. A reduced-quality older recording may not support the same investigation task as recent full-quality footage.

2. Collect the inputs that actually affect the estimate

The basic calculation uses camera count, average recorded bitrate, recording hours per day, and retention days. Use measured or manufacturer-estimated average bitrate for the intended settings. Megapixels alone do not determine the amount of recorded data.

For event recording, hours per day means expected recorded time, including any pre-event and post-event periods. A quiet test day can understate a busy location's workload. Create a second scenario with more activity so the purchasing decision does not depend on one optimistic assumption.

3. Understand the storage calculation

Estimated video storage in decimal terabytes equals cameras × average Mbps × recording hours per day × retention days × 0.00045. The factor converts megabits to bytes, hours to seconds, and bytes to decimal terabytes. It describes the video payload under the entered assumptions.

Eight cameras averaging 4 Mbps, recorded continuously for 30 days, estimate 10.368 TB: 8 × 4 × 24 × 30 × 0.00045. Reserving 20% of capacity as free space requires 12.96 TB: 10.368 ÷ 0.8. This illustrative reserve is a planning choice, not a manufacturer requirement or guarantee.

• Doubling the camera count or retention period doubles the estimate when other inputs stay fixed.
• Reducing recording hours lowers the estimate only if actual recorded activity follows that assumption.
• Divide estimated storage by (1 − reserve percentage ÷ 100); calculate RAID and filesystem overhead separately.

4. Calculate different camera groups separately

An entrance, a quiet storage room, and a busy outdoor view can have different bitrates and recording schedules. Calculate each group separately and add the results. Keep a list of the settings behind each group so a later resolution or frame-rate change triggers a new estimate.

Variable bitrate and scene-aware compression respond to image content. Axis documents that Zipstream can use different bitrates as scene activity changes. Lighting noise, movement, and image settings therefore matter when checking actual usage. Do not apply a generic compression-saving percentage to every camera without evidence from the proposed configuration.

5. Translate the estimate into usable recording capacity

Ask the supplier to show raw disk capacity, capacity after any redundancy configuration, and capacity actually available to recording. Decimal TB and binary TiB displays also differ. Keep all comparisons in a consistent unit, and include audio, additional recorded streams, metadata, or other overhead where the system requires it.

Check write throughput and recorder camera limits as well as capacity. More disks do not automatically remove a processing or network bottleneck. Systems such as UniFi Protect expose retention settings, while other platforms use model-specific storage options; verify the final design with the selected platform's tools.

6. Verify actual history after commissioning

After representative operation, compare measured storage use and the oldest accessible footage with the design assumptions. Check the required views and image quality, not just a dashboard's estimated days. Repeat the review after adding cameras or changing recording settings.

Keep the original calculation, final configuration, measured results, and any adjustments together. If the target is missed, agree whether capacity, settings, or the requirement should change. Avoid silently reducing useful image detail to make an advertised number of days appear achievable.

Common questions