To echo Tom's question, what do you want to do with the size you are reporting on? I would caution you that it could be misinterpreted. If you just want, for example, month-to-month growth figures so you can see which tables are growing over time, then dbanalys output will give you that.
But don't expect the actual numbers to correspond to the amount of disk space used by the data in question. Depending on your structure, there could be a significant difference between the two.