If you want to tell someone to relax and calm down, there are many ways to say it using synonyms for the phrase "chill out." Some examples include:
1. Calm down
2. Take it easy
3. Cool off
4. Unwind
5. Ease up
6. mellow out
7. De-stress
8. Take a breather
9. Kick back
10. Keep calm
11. Relax
12. Be at ease
Using these synonyms can help convey the message in a more casual or friendly manner and can show that you're concerned with their well-being. So, next time, don't hesitate to tell your friends or loved ones to chill out in a variety of different ways!