How much swap is being used on windows?

In task manager, the "page file usage" is actually the system commit total, which is not the same thing as page file usage. In 2008, MS changed the wording to more accurately reflect what was being measured, which is actually the amount of reserved virtual memory.

To get the actual amount of PageFile usage, open up Performance Monitor (perfmon), and Add Counters (The button with the "+" icon, 8th over, left of the X") -> Paging File -> % Usage and/or % Usage Peak. It's going to be a lot lower than the reserved value displayed in Task Manager... at least if you have any meaningful amount of RAM in your system.

STEP BY STEP solution

Note: These are the exact steps for Win 7. I think is the same on Win 8.

To get the actual amount of PageFile usage, start 'Performance Monitor' (perfmon.exe) and go to

Add Counters -> Paging File -> Usage

It will give you the answer in %, but you know the total amount of paging file so you can calculate the exact amount of USED paging file (in MB).

To read the total amount of paging file:

Press Win+Break keys to open 'System properties'.
Go to:

Advanced -> Performance -> Advanced -> Virtual memory -> Total paging file size

(size will be in MB).