How much disk and what box do I need?
Work out the storage, the memory and the machine from how many cameras you have and how long you want to keep them.
Work it out
Answer four things and this gives you the disk, the memory and the class of machine. Nothing here is asked that you would have to look up: the bitrate the sums need is carried by the quality choice, and shown under Advanced if you want to change it.
What the Hub records unless you tell it otherwise. Measured between 0.4 and 1.5 Mbps across the reference cameras.
These are a starting point, not a promise. On the reference hub two cameras of the same model shipped substreams three times apart, so no table can tell you what your own footage costs. Your Hub reads the real bitrate off each camera and answers this properly before you turn recording on.
Why bitrate and not resolution
Storage is decided by how much data a camera sends each second, and that is not a function of resolution. On the reference hub two cameras of the same model shipped substreams three times apart, so a figure worked out from a resolution table would have been wrong for one of them.
Codec matters more than pixel count too: H.265 is roughly half the size of H.264 for the same picture, which is why a 4K camera in H.265 can cost less disk than a 1080p one in H.264.
Your Hub reads the real bitrate off each camera and can tell you what your own footage costs before you switch recording on. That number beats anything on this page.
Why recording is cheap and watching is not
Recording is a copy. The Hub never decodes what it writes, which is why a box recording sixteen cameras sits at a few percent of one core and its own processes stay under 60 MB. No GPU is involved.
Showing cameras is the opposite: every tile on a wall is decoded. That is where memory and a hardware decoder start to matter, and why the Hub caps how many tiles a class of box will drive. The caps in the calculator come from the Hub's own host registry, so this page and your Hub agree.
Seven cameras recorded and watched at once cost about 2% of a Raspberry Pi 5, and about 50 GB a day. The board is almost never the constraint; the disk is.