Well, the actual size of your rows depends on a data that is in them. By merely looking at datatype of your columns you can't conclude how much space the row will occupy. One row in a table could occupy only 1 byte, while the other row in the *same* table could occupy hundreds or thousands or milions of bytes!

- For character datatypes, the space occupied by data depends on the database characterset, but usualy the number of bytes will be equal to the length of the contained string (for CHAR it will be equal to the length of the column).
- For dates it will always be 7 bytes.
- Boolean is not a database type, so you won't have any column of that type.
- For numbers it is a little tricky to calculate the space they consume. For example, 1,000,000,000 will ocupy (much) less space than 1.923968. You can find an actual formula to calculate the required number of bytes for each number in Oracle Concepts manual.
- Any null value (of any data taype) requires 1 byte of space, unless there are only null values in all following columns to the end of the records, in which case it does not ocuppy any space at all.

In any case, you can use a VSIZE() function to find out the number of bytes occupied by any calumn value.