How many tandem breakers are you allowed to have in a main panel box? Is there a certain # allowed? For example, if you have a 30 space main panel box, how many of the 30 standard breakers can you change to tandem breakers?

Battle

Depends on the panel, otherwise look for a "maximum number of poles" specification somewhere. Some panels physically restrict their use in certain positions. They may not be available for the panel, either.

Find the "maximum number of poles" and # of spaces spec for your panel and get back.

How many tandem breakers are you allowed to have in a main panel box? Is there a certain # allowed? For example, if you have a 30 space main panel box, how many of the 30 standard breakers can you change to tandem breakers?

Battle

Do you know what type of panel you have? Siemens panel etc? And what the amps is for the whole service?