What is Total/Available Virtual Memory?

Speccy shows on my PC:
Physical Memory
----------------------
Memory Usage 43 %
Total Physical 7,91 GB
Available Physical 4,48 GB
Total Virtual 16 GB
Available Virtual 12 GB
pagefile.sys 7.9 GB
What is total/available virtual and how does Speccy calculate it?

Total phyical minus used amount equals available

In your case

7.91 - [.43(7.91)]=4.48

Total phyical minus used amount equals available In your case 7.91 - [.43(7.91)]=4.48

thank you but I asked about the virtual memory not the physical!

Sorry I misread it. Maybe this helps

http://windows.microsoft.com/en-us/windows/what-is-virtual-memory#1TC=windows-7

Total Virtual = Total Physical + pagefile.sys