How can I easily find out the *size* of an object? And so max users my app can take..

[Brian Blesbok]

Hi everyone,
Just wondering if there is a way of getting how many bytes an object takes up - I'm thinking in terms of session managment issues and user management - and how I can plan (on paper) how many users my app will be able to handle...?!?!?
Cheers for the anticipated help!
B