CCTV Storage Calculator Guide: How Much Recording Space Do Your Cameras Need?

Start with the TSS CCTV storage calculator

Use the TSS CCTV Storage & SD Card Calculator to build an estimate from your camera count, bitrate, recording schedule and retention target. The calculation is most useful when those inputs reflect your actual configuration. Do not use a megapixel label as a substitute for checking the recording settings.

Decide what you need first: seven days of continuous video, a month of event clips or another specific retention period. The answer affects both capacity and recording design. A large drive does not guarantee that the recorder accepts it or that a memory card supports the required workload. Confirm the full combination before purchasing storage.

Why bitrate matters more than resolution alone

Bitrate is the amount of data recorded each second. Two cameras with the same resolution can generate different storage loads because of compression, frame rate, image complexity and quality settings. A quiet indoor view and a busy outdoor scene with moving foliage are not equivalent workloads.

Compression names such as H.264 or H.265 indicate encoding families, not one fixed storage saving. Settings and scene content affect the result. Avoid claiming that switching codec always halves capacity. Measure a representative sample when possible, especially if retention is important.

Check whether the recorder captures the main stream or another stream. The recording stream can differ from the stream used for phone viewing. Use the bitrate of the footage actually saved to storage. Include audio if it is recorded, and consider any additional streams retained for analytics or other functions.

The calculation, with clear units

For continuous recording, the approximate data size is bitrate multiplied by seconds, divided by eight to convert bits to bytes. Using decimal units, one camera at 4 megabits per second produces about 43.2 gigabytes per day: 4 multiplied by 86,400 seconds, divided by eight, then divided by 1,000.

For four cameras at that assumed bitrate over 14 days, the estimate is 43.2 multiplied by four multiplied by 14, or 2,419.2GB, about 2.42TB before allowances. This is an arithmetic example, not a specification for every 4K or four-megapixel camera. Replace 4Mbps with your actual recorded bitrate.

The calculator and recorder may display decimal TB or binary units differently. A drive sold as 4TB can appear as a smaller numerical capacity in software without having lost physical storage. Formatting, reserved areas and system overhead also affect usable capacity. Keep the unit convention visible when comparing estimates and hardware.

Continuous, scheduled and motion recording

Continuous recording is easier to estimate because the recording duty cycle is known. Scheduled recording reduces hours, but only if the recorder truly stops saving footage outside the schedule. Check whether event recording continues separately and whether the schedule applies to every channel.

Motion recording depends on activity. A camera watching a busy road can generate much more footage than one looking at a quiet back door. Pre-event and post-event buffers also add recording time, so “motion happened for ten per cent of the day” does not automatically mean exactly ten per cent of continuous storage.

For a conservative first estimate, calculate continuous recording and then examine whether a lower duty-cycle assumption is justified. If relying on event recording, verify detection and ensure it captures the events you need. Reducing storage consumption is not useful if it removes the important evidence.

Worked examples to compare

Capacity headroom and measured verification

Leave headroom for variation and system use rather than choosing a drive that only just matches the calculation. The appropriate allowance depends on recorder behaviour, bitrate mode and how closely the input represents real conditions. Explain your allowance instead of presenting an arbitrary percentage as a manufacturer requirement.

After commissioning, check how much space a representative day consumes and how far back the recorder can retrieve footage. Include busy periods and night scenes. Variable-bitrate recording can produce different volumes over time, so one unusually quiet hour is a weak basis for a month-long retention promise.

If retention is a contractual or operational requirement, document the settings and test the result. A change to frame rate, camera count or image quality can invalidate the original estimate. Recalculate after adding cameras and keep a record of the configuration used for the capacity decision.

Selecting a compatible surveillance drive

Compare these relevant TSS products using the current specifications on their pages: Seagate SkyHawk 2TB SATA 64MB (ST2000VX017), Seagate SkyHawk AI 8TB 3.5" SATA (ST8000VE001). Availability and fulfilment details can change; confirm them before ordering.

Seagate SkyHawk and SkyHawk AI products are relevant surveillance-storage examples. Match the exact model and capacity to the recorder manufacturer's approved specifications, including drive-bay count, interface, maximum per-drive capacity and any total capacity limits. A surveillance label does not make every drive compatible with every NVR.

The TSS 2TB SkyHawk listing and 8TB SkyHawk AI listing provide distinct options to review. Do not assume their capacities solve the worked examples without considering usable space and recorder support. Also check the precise model code on the live listing, because legacy URL text can differ from the current product title.

For cameras that record to microSD, check maximum supported capacity, endurance requirements and the manufacturer's approved card guidance. Ordinary capacity alone does not describe write endurance. A card and a recorder hard drive serve different environments and should not be treated as interchangeable storage options.

Retention, export and backups are separate

Rolling storage normally overwrites the oldest footage when its allocated space is full. Keeping 30 days of recordings is not the same as retaining a critical clip indefinitely. Export important footage promptly using a supported format and check that it can be played back on another device.

RAID, where supported, can improve resilience to certain drive failures, but it does not replace an independent copy of required evidence. It also changes usable capacity. Use the relevant RAID calculation and recorder instructions instead of adding the raw capacity of every installed drive.

Our home camera planning camera-coverage guide helps establish how many views your property needs. The CCTV calculator then helps translate that design into a transparent storage budget. Choose storage from verified settings and compatibility, and validate real retention after installation rather than treating the calculator output as the final test.

Frequently asked questions

How much space does one 4K camera use?

Resolution alone is insufficient. Check recorded bitrate, frame rate, codec, scene and recording schedule. Enter those details into the calculator for a useful estimate.

Does H.265 always halve storage?

No. Compression savings depend on settings and scene content. Use measured or documented bitrate rather than applying one guaranteed percentage to every camera.

Does motion recording use ten per cent of continuous storage?

Only if the actual saved duty cycle is ten per cent under comparable conditions. Buffers, false events and busy scenes can increase the saved volume substantially.

Can I fit any large hard drive into my NVR?

No. Check interface, maximum capacity, supported models and recorder firmware guidance. Capacity is only one part of compatibility.

Size CCTV storage with TSS

Browse TSS security cameras and equipment and compare the exact model details before you choose. For help matching equipment to your setup, contact Tech Supply Shed with your current model and requirements.

Sources and further reading

Technical references checked on 2 October 2026: Seagate surveillance-storage calculator