Steps to check the CPU usage on a Windows 8 / 8.1 computer:
Step 1: Open Task Manager.
On the Start or Desktop screen, press Windows key + R for a while to open the Run window, type taskmgr in the box, and click OK.
Step 2: Check CPU usage.
In this step, you can check the CPU usage of a particular program or game and learn about the full CPU usage. Please refer to the following method.
1. In Processes, check the CPU usage of a particular process you want to know in the CPU column, as shown in the figure below.
2. Select Performance in Task Manager, and you can see all CPU usage in the upper left or see it in the middle.
Therefore, with just two steps, you can check the CPU usage efficiency on your computer. Alternatively, if you want to check if your computer’s CPU is up to your needs, you can open some of the major apps and games and limit their CPU usage. Assuming CPU usage exceeds 90%, it shows that the CPU should be upgraded to meet your requirements.