If you want to know what frame rates your Steam games are running at, there are many third-party programs out there to help. But if all you need is a very basic counter and you don’t care about other hardware stats, you don’t need to download any of these — you can use a feature that’s built right into Steam.

Here’s how to set up Steam’s built-in FPS counter for your PC.

• Open Steam.
• Go to Steam > Settings > In-Game.
• Under In-game FPS counter, select the corner where you’d like the counter to appear. You can also check High contrast color if you prefer.
• Click Ok.

Now, go ahead and start your game. You should see the frame rate your game is running at displayed in the corner that you specified.

https://www.theverge.com/23283921/steam-fps-counter-how-to