CCTV Video Storage Calculator
Work out how much disk a system really needs — with the mix of cameras you are actually installing. Free, no signup, and nothing leaves your browser.
The cameras
2.16 Mbps each · 17.3 Mbps for the group
The recording
8 cameras · 30 days
5.60TB of footage
- Per day
- 187 GB
- As the recorder reports it
- 5.09 TiB
- Stream bandwidth
- 17.3 Mbps
What to buy
1× 8 TB drive
That is 8 TB on the box and 7.28 TiB once the recorder has it, against the 5.09TiB this system writes. Drives are sold in decimal terabytes and reported in binary ones, so a “8 TB” drive shows up as 7.28 TiB — about 9% less. Sizing off the number on the box is how a 30-day spec quietly becomes 27.
This is the footage only. Leave room for the operating system, for RAID parity if you are using it, and for the fact that every estimate here is an estimate.
How this is worked out
Bits per pixel. A codec spends roughly a fixed number of bits on every pixel it encodes, so bitrate follows pixels per second and everything else is a multiplier. The baseline here is 0.064 bits per pixel for H.264 at 30fps on a typical scene, which is what published manufacturer figures work out to: about 4 Mbps at 1080p, 7 at 4MP and 16 at 4K. Those agree to within 2% across a four-fold range of resolution, which is what makes one constant honest rather than a fudge.
Frame rate is not linear. Halving the frame rate does not halve the bitrate — with fewer frames there is more change between each one, so every remaining frame costs more to encode. We scale by roughly the 0.85 power, so 15fps lands near 55% of 30fps rather than 50%. A calculator that scales straight down under-sizes every low-frame-rate system, which is most retrofits.
Codec. H.265 is usually sold as half the bitrate of H.264; we use 0.55, the conservative end of what it delivers on surveillance footage. The smart-codec variants — H.265+, Zipstream, Smart Codec — go further by dropping the bitrate hard on static scenes, which is real but depends entirely on the scene staying static, so we use 0.35 rather than the headline number. Sizing a recorder on a vendor best case is how a system runs out of disk in month two.
Terabytes and tebibytes. Drives are sold in decimal terabytes and reported by the recorder in binary tebibytes, and the gap is about 9%. We show both, and we size the drive count against the smaller one — because a recorder fills up when its own accounting says it is full, not when the box says so.
Bandwidth ignores the duty cycle, deliberately. Recording on motion writes less to disk. It does not make the cameras stream any less: they are sending video to the recorder all day regardless. Size the switch and the uplink off the full figure, which is the one shown.
Common questions
- How much storage do 16 cameras need?
- It depends far more on resolution, frame rate and codec than on the camera count. Sixteen 4MP cameras at 15fps on H.265, recording continuously for 30 days, comes to about 11 TB. The same sixteen at 4K and 30fps on H.264 is about 83 TB. That seven-fold spread is why a number from a rule of thumb is worth very little and why this asks for the mix you are actually installing.
- Why does the recorder show less space than the drives I bought?
- Because drives are sold in decimal terabytes and reported in binary ones. A 4 TB drive holds 4,000,000,000,000 bytes, which the recorder counts as 3.64 TiB — about 9% less. Size a job off the number on the box and a 30-day retention spec quietly becomes 27 days. This calculator shows both figures and sizes the drive count against the smaller one.
- Does recording on motion only really halve the storage?
- Rarely. A motion trigger on a car park or a street fires most of the day, and a site that records 20% of the time during a quiet survey week records far more at Christmas. Guess high — and note that motion recording does not reduce the bandwidth at all, because the cameras stream continuously whether the recorder is writing or not.
- How accurate is this?
- It is an estimate built on bits per pixel, anchored on published manufacturer bitrate figures for H.264 at 30fps, which agree to within 2% across a four-fold range of resolution. Real bitrate still depends on the encoder, the scene and the camera's own quality setting. Use it to size a recorder with headroom, not to predict a number to the gigabyte.
Where the camera count comes from
The hard part of this sum is not the arithmetic, it is knowing how many cameras and at what resolution. That comes off the floor plan. FieldMarkup puts the cameras on the drawing with their coverage to scale, and the device schedule that falls out is the input to this page.