Windows 8.1 Experience Index

Find your Windows Experience Index scores in Windows 8.1 - CNET
The Windows Experience Index benchmark tool is harder to find in Windows 8.1,
but is still available if you know where to look.

Open a command prompt as administrator, then type "winsat prepop" and press Enter.
This will run the benchmark and store the results on your PC as XML files.

Open the Windows Powershell as administrator, then type
"Get-WmiObject -Class Win32_WinSAT" and press Enter.
This will analyze the results in the XML files, then present them as scores for each category

.