>I have a database A in Server 1
>data size is 1200MB. data space available is 655MB. I calculated the actual size of the 1200-655 = 545 MB.
>
>Is this correct?

Not necessarily. You've not accounted for the possibility of fragmentation.

>How can I compare two database to know they are same?

"Same" what? Size? Data? Schema?

-Mike