Licensing MS SQL 2016

I'm new to licensing and its doing my head in understanding how many CALs I need for an installation.
Hopefully someone can make this simple for me.

Intending to use SQL server 2016 with server/CAL licensing.
Single standalone server with 24 cores.
SQL Management Studio will be used on this server.
The SQL server connects to a single Win 2012 intranet/web server (also 24 cores).
Only two users can log into the web app at any one time.
There will also a database update app running occasionally on the web server processing some external data to update the dB.

Is this 4 CALs total?