How often are you subnetting, or just trying to get valid sets of CIDR (classless inter-domain routing) addresses?
For that there are a bunch of online tools, but the one tool I prefer is the ipcalc command line tool. The Linux man page is here: ipcalc man | Linux Command Library
It's also available on macOS using Homebrew via
brew install ipcalc – and there is an online-version here: http://jodies.de/ipcalc
Full source is here: ipcalc / ipcalc · GitLab
An example might be, lets say you have a segment that needs to have 16 addresses per subnet. Just ask
ipcalc 10.0.0.0/16 -s 14