CCTV Storage Calculator

Everything about camera storage follows from one rate: bitrate, in megabits per second. Multiply bitrate by the seconds in a recording day (3,600 × hours), divide by 8 to turn bits into bytes, then by 1,000 to get decimal gigabytes. A 4 Mbps 1080p stream running 24 hours lands at exactly 43.2 GB per camera per day. Multiply by cameras, by retention days, and by 1.10 for file-system overhead — the structures a drive maintains around the footage — and you have total capacity needed.

The decimal-vs-binary distinction is not pedantry here. Drive manufacturers label in decimal units (1 TB = 1,000 GB), while operating systems sometimes report binary tebibytes (1 TiB = 1,024 GiB), which makes a drive look about 7% smaller after formatting. This calculator works in decimal throughout so its answer lines up with the number printed on the retail box; the +10% overhead absorbs formatting and index structures on top of that.

Bitrate is the lever you actually control. Resolution and codec set a starting point, but most recorders expose a bitrate slider per camera — dropping from 6 to 4 Mbps cuts storage by a third at a quality cost most people never notice on playback. The calculator's custom bitrate field exists for exactly this: read the configured rate off your NVR's stream settings and the estimate matches your system instead of a generic preset.

H.264 and H.265 describe how cameras compress video, and H.265 is simply the newer, thriftier of the two: roughly the same image from about half the bits. The presets reflect common real-world pairings — 1080p at 4 Mbps on H.264 or 2 Mbps on H.265; 4 MP at 6 or 3; 4K at 8 or 4. For a four-camera 1080p system retaining 30 days, that is 5.7 TB versus 2.9 TB — one drive size tier apart on the standard ladder.

The honest trade-offs: H.265 demands more from the camera and the playback device (older phones decode it poorly), licensing surfaces occasionally in odd places, and mixing codecs across a system complicates export. Most 2019-and-later kits handle it fine. If in doubt, size with the H.264 preset — buying one tier more drive than you need is cheaper than re-buying cameras.

Bandwidth deserves a glance too: bitrate times cameras is the network load your Wi-Fi or switch carries. Eight 4K cameras on H.264 push 64 Mbps — beyond many mesh networks' real throughput back to the NVR. The calculator's bandwidth line tells you when it is time to run cable.

This tool's numbers assume continuous recording: every camera, every second of its scheduled hours. That is the conservative basis for a drive purchase, and the right one for most security retrospectives — you can scroll to any timestamp. Motion-only recording replaces idle time with nothing, and on a quiet property it can stretch the same drive several times further; on a busy street it saves much less than people hope.

The practical middle path most installers land on: continuous at a modest bitrate, plus a higher-quality or higher-fps profile triggered by events. Size the drive on the continuous number — this calculator — and let motion events ride on top; the +10% overhead covers the burst indexing. If you go motion-only, treat the calculator's output as your worst case and enjoy the surplus months of retention.

Two final buying notes: choose surveillance-rated drives (firmware tuned for 24/7 writes rather than desktop power-saving), and leave physical room to grow — retention requirements have a way of stretching from two weeks to two months after the first time footage is actually needed.

Estimates use preset bitrates and decimal units; actual consumption varies with scene complexity and recorder settings. Verify against your NVR's own calculator before purchase.