How can I calculate my net income in Germany? Given a salary of 40kEUR, how can I know how much I'll take home?
There are many sites to run a simulation. You need to know that the gross (pre-tax) salary is called “Bruttolohn” and the take-home pay is your “Nettolohn”. Looking for “Gehaltsrechner” returns many results, among other:
As you will notice, there are a few complications as your take-home pay will depend on your province (Land), whether you choose for private or public insurance (you can only choose if your salary is above a particular threshold) and whether you have a partner or kids (which also determines your Lohnsteuerklasse).
Take home pay will depend on your tax class and a few other things. Take a look at this calculator. It has short explanations about tax categories or any other configurable thing.