Row count where data exists

Row count where data exists

I am new to learning VBA and was wondering if someone could help me with
the code I need to count the total number of rows that I have with data in
them. I want to be able to use this on multiple sheets with different
amounts of data rows.
More specifically I cannot figure out generic code that will count the
number of rows from A1 - A100 or A1- A300.
Right now I am trying to use something like this, but it does not work. i
= ActiveWorkbook.Worksheets("Sheet1").Range("A2 ,
Range("A2").End(xlDown)).Rows.Count
Please help!
Thanks