How to see available space when burning a disk?

Please can someone tell me how I can see how much space is left on a blank disk when I am adding files to burn? In Windows there is a clear indication at the bottom of the screen showing how much space is left on the disk, so you can calculate which files/folders will fit into the space left. On my Mac there seems to be nothing - or at least nothing I can see in the Finder window - so how am I supposed to know when the disk is full or not? I usually end up putting too much on there & then it tells me once the burn process has started that there isn't enough space. This isn't very helpful or practical. Any advice appreciated....