420 ml according to Brack / according to piccantino ~ 1/2 litre. I can tell you that for a "normal" cup for me, it is only enough for 2 to max. 3 cups. Here, "9 cups" probably means espresso cups. Hope that helps you :)

I can agree with the previous speaker, you can basically divide the Bialetti specifications by three and then have a "normal" cup for us Swiss.