Oracle Database Discussions

Hello,

My boss required me to make an estimate about an oracle database size.
This database still doesn' t exist...
He (my boss) will supply me with the number of tables and the approach number of records in each table this database will have, and then I must be able to calculate an estimated size for this database in bytes.
It is just an estimate, this size doesn't need to be precise.
Is this possible? How can I give to my boss an estimated size for this database? How do I calculate this?

I hope somebody will help me.