It's important to check your computer's CPU usage to make sure it's operating normally. Georgijevic/Getty Images You can check your CPU usage on a PC with the Task Manager or Resource Monitor apps. On a Mac, you can check your CPU usage using the Activity Monitor app. Your CPU usage tracks how hard your computer is working to run programs, make calculations, and more. Visit Insider's Tech Reference library for more stories. Your PC or Mac's central processing unit (CPU) is like its brain.