CCTV Storage Calculator

Analog vs. IP — why storage math differs

Older analog HD-CCTV systems (recorded through a DVR over coax cable, using AHD, TVI, or CVI signaling) top out at lower resolutions and typically only support H.264 compression — no H.265 or smart-codec options. IP camera systems (recorded through an NVR over network cable) support far higher resolutions and modern codecs. This calculator switches its resolution list and codec options based on which type you pick, so the bitrate estimate matches your actual hardware.

Worked example

Illustrative only — your actual result depends on your own camera count, resolution, fps, codec, recording mode, and retention. This is one example, using the calculator's own default inputs, not a rule of thumb for every job.

IP camera system, 8 cameras, 4MP resolution, 15 fps, H.265, continuous 24/7 recording, 30-day retention.

Analog HD-CCTV resolution reference

IP camera resolution reference

Source note: the roughly 50% figure for H.265 matches what the ITU said when it announced the standard, that HEVC "will need only half the bit rate of its predecessor" (ITU press release, 25 January 2013). That was a projection by the standards body, not a measurement of CCTV streams. The H.265+ and smart-codec savings used on this page are planning estimates without a verified source, and they vary heavily with the scene.

Upgrading from analog to IP?

If you're quoting a system replacement (swapping an old analog DVR setup for IP/NVR), run the numbers for both system types with the same camera count and retention period — it makes the storage-capacity jump concrete for the customer, not just a "better picture quality" pitch. For network sizing on the IP side, follow up with the IP Camera Bandwidth Calculator to size the switch and NVR ports.

Decimal TB vs. what your OS displays

Hard drive manufacturers advertise capacity in decimal terabytes (1 TB = 1,000,000,000,000 bytes), which is also the convention this calculator uses for its TB figures. Operating systems typically report capacity in binary units, which shows a smaller number for the same physical drive — roughly 7–10% less — and formatting/filesystem overhead reduces the usable amount further still. A 6 TB drive showing as roughly 5.45 TB or less in your NVR or OS is expected behavior, not a sign of a faulty or short drive.

Drive bays, RAID, and this calculator's limits

This calculator gives you the raw storage figure — it doesn't know your recorder's physical limits. DVR/NVR storage capacity is also bounded by the recorder itself: every recorder has a fixed number of SATA bays and a per-bay drive-size ceiling set by its firmware, so a theoretical 20 TB recommendation is meaningless if your recorder only has two bays rated for 10 TB drives each — check your recorder's datasheet before buying drives. Redundancy (RAID 1/5/6) is a separate infrastructure decision this calculator doesn't model as a full RAID engine — RAID trades some of your total capacity for fault tolerance, so if you're specifying RAID, size your drives above this calculator's raw figure to leave room for that overhead.

Working backwards: how long will my drive last?

The same bitrate-to-storage relationship works in reverse: once you know your camera count, resolution, fps, codec, and recording activity, you can estimate how many days a drive of a known size will hold before it fills up — roughly, drive capacity divided by the "storage per day (all cameras)" figure above. This calculator doesn't solve for retention days directly; run your setup above to get that per-day figure, then divide it into your drive's capacity for an estimate.

For example, using this page's own default setup — 8 cameras, 4MP, 15 fps, H.265, continuous 24/7 recording — storage works out to about 168.5 GB per day for all 8 cameras combined. A 1 TB drive would hold roughly 1,000 ÷ 168.5 ≈ 5.9 days of footage, and a 4 TB drive roughly 4,000 ÷ 168.5 ≈ 23.7 days. These figures apply only to this exact setup — change the camera count, resolution, fps, codec, recording mode/activity, or recording hours per day, and both the storage-per-day figure and the number of days a 1 TB or 4 TB drive lasts will change with it.

Frequently asked questions

Should I use this or the NVR Storage Calculator?

Use this one if any part of your job includes analog HD-CCTV (DVR, coax, AHD/TVI/CVI) hardware. If it's a pure IP camera install, the NVR Storage Calculator gives the same result with a simpler resolution list.

Why doesn't the analog side have codec options?

Analog HD-CCTV hardware is effectively locked to H.264. DVRs and coax-based cameras don't support H.265 or smart codecs, so the codec toggle only appears when you select an IP system.

How accurate are the analog bitrate figures?

Less precise than the IP figures. Analog HD-CCTV bitrates vary more by manufacturer than IP camera bitrates do, so treat these as a solid planning estimate and confirm against your specific DVR's datasheet before ordering a drive for a large or long-retention job.

Does H.265 reduce CCTV storage requirements?

Yes — H.265 (HEVC) typically needs roughly half the bitrate of H.264 for comparable video quality, and H.265+/smart-codec variants can reduce it further on scenes with limited motion. Actual savings depend on the specific camera, scene complexity, and encoder implementation, so treat the codec factors in this calculator as planning estimates rather than guaranteed numbers.

Does motion-detection recording reduce storage?

Yes, in principle — motion-triggered recording only writes to disk when the camera detects activity, so less continuous recording time means less storage used. How much it actually saves depends entirely on how much activity the camera sees, so the "estimated recording activity" percentage in this calculator is a planning estimate you set based on your scene, not a value the calculator or the camera can guarantee.

How does frame rate (FPS) affect CCTV storage?

Lower fps reduces bitrate, but not in a straight line down to zero — this calculator scales bitrate between 30% and 100% of its 30fps figure as fps drops from 0 to 30, since full reference (I-)frames still need to be recorded at intervals regardless of frame rate. Halving fps from 30 to 15 typically saves noticeably less than half the storage, not exactly half.

Why is my hard drive's usable capacity smaller than advertised?

Hard drive manufacturers list capacity in decimal terabytes (1 TB = 1,000,000,000,000 bytes) — the same convention this calculator uses. Operating systems typically report capacity in binary units, which shows a smaller number for the same physical drive (roughly 7-10% less), and formatting/filesystem overhead reduces the usable amount further. A 6 TB drive showing as roughly 5.45 TB or less in your NVR or OS is expected behavior, not a faulty or short drive.

Related CCTV tools

A pure IP install can use the NVR Storage Calculator instead, which covers the same math with a simpler resolution list. On the network side, the IP Camera Bandwidth Calculator sizes your switch uplink, and the Field of View Calculator confirms camera placement and coverage.

Related guide

Not sure whether analog or IP is the right call for this job in the first place? See Analog vs. IP CCTV in 2026: Which Should You Actually Install for a balanced breakdown of when each one genuinely makes sense.

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