Here's an online calculator. They give no warranty and they emphasize that it's just an estimation. If you want exact figures, you'll have to contact the authorities. As you can see, the number depends on the time spent in Switzerland, marital status and some other factors.


Edit: The online calculator does a referrer check. To get to the correct website, it is necessary to do one of the following two things:
a) Go to this website and click on "Theoretische Rentenabschätzung"
b) Open a new, empty browser window and paste the following URL:
http://www.ahv-services.ch/reschweb/rentenform.aspx