Check if your Mac needs more RAM in Activity Monitor
The Memory pane displays how much memory your Mac is using, how often it is swapping memory between RAM and your startup disk, and the amount of memory provided for an app and how much of it is compressed memory.
When you have free or unused memory, your computer performance does not necessarily improve. macOS obtains the best performance by efficiently using and managing all your computer’s memory.
In the Activity Monitor app
on your Mac, click Memory.The Memory Pressure graph lets you know if your computer is using memory efficiently.
Green memory pressure: Your computer is using all its RAM efficiently.
Yellow memory pressure: Your computer might eventually need more RAM.
Red memory pressure: Your computer needs more RAM.
If memory pressure is yellow, red, or has spikes, check to see if an app is using up memory and causing the memory pressure to increase. If you no longer need to have the app running, you should quit the app.
Your computer’s memory pressure is accurately measured by examining the amount of free memory available, the swap rate, and the amount of wired and file cached memory to determine if your computer is using RAM efficiently.
To learn whether you can add RAM to your Mac, press and hold the Option key, then choose Apple menu 