I know, this is very basic principles (and I tried that with cameras that show all H/V/D options) but not quite working, hence why I asked.
IPC-HDW5442T-ZE shows Field of View: Horizontal: 114°–47°, Vertical: 62°–26°, Diagonal: 136°–54°, and using the formula for 114 and 62, gives me 129.8...