How do you calculate historical growth rate?

It depends on what you are measuring; growth in sales or appreciation (depreciation) in stock price is pretty straight forward. Growth in portfolio value on the other hand can involve additional mathematical steps if there are deposits (withdrawals) within a period (i.e. monthly, quarterly). You would get a much more meaningful answer if you added more detail to the question.

An example would be a great help to someone trying to provide you an answer.