In order to know the volume of your hard drive you have to use one of these methods:
Standard way to check Disk Space
- Find in an upper left corner of the screen.
- Choose About This Mac item.
- In appeared window choose Storage section.
Here you can see an amount of available storage, an amount of occupied space, distribution of memory by file types and supported disc formats.
Check Disk Usage with Disk Expert
If you have to have a clear picture of your disk space, you can also use Disk Expert. With it, you can see a detailed diagram of your hard drive space distribution as well as of any other media (including hidden files and folders).