Chill out!

Calm down!
Relax!
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Are they the same in meaning? Do you have some other similar expressions?

Yes, they are all the same meaning. There are other ways to say it, I suppose. I could say I'm having a quiet evening at home, or "chilling out" at home, or "relaxing" at home, etc. Chilling out is a slangy way of saying it. We might also advise someone to "take deep breaths" to calm down or chill when someone is angry or excited or fearful, etc.