Check Actual DB Size

Hi,
How do I check what is the actual DB size that is currently being use?
e.g. I set 10 GB as initial size. A few days and a few transactions later, how can I know how much was used since it is still under 10GB and checking the physical DB file will not tell me anything.If you are looking for SQL SERVER.
I think when u create it for the first time it creates a database of 2 GB.

If Enterprise Manager, select the Database name that you are looking for.
Right Click and check for Properties.

You get 2 Options : Size : 2 GB
Size Available : 0.98 GB.

Is this the Information that you are looking for|||ooh..okay..thanks...
But anybody can confirm that I just need to check from there?

I checked one of the db...the available size was 0.00mb but the Size is 40mb....this db was originally detach and ziped from Production enviroment and unziped then attached to Development.