Replacing a main panel is not a DIY project in my opinion (not even allowed in my area).
However, if you are trying to get a general idea you need to run a demand load calculation.
is a link to one. there are many others. search past threads as well.
Keep in mind you cant just replace say a 100amp panel with a larger 200a panel -- the service size probably has to change. this is an even more major project that is beyond the reach of "almost" every DIY
Not blowing you off - people here can help you estimate your service size requirements if you provide more detail.