Estimate size of database based on schema

It would be great if there were a way to estimate the storage space needed to store each table in the schema.

For example, depending on how many columns and their types you can estimate how much storage a row in each table will require and then project that out to 500,000 rows.

I realize it gets tricky with indexes, different server technologies, etc. but an estimate of raw data storage might help when looking for opportunities to reduce data duplication.