calm down vs chill out

calm down and chill out both are verbs.

Word	Noun	Adjective	Verb	Adverb
calm down	No	No	Yes	No
chill out	No	No	Yes	No

As verbs, calm down and chill out are synonyms defined as:

calm down and chill out: become quiet or calm, especially after a state of agitation

Other synonyms of calm down include calm, cool it, cool off, settle down, simmer down.

calm down (verb)	chill out (verb)
become quiet or less intensive	become quiet or calm, especially after a state of agitation
make calm or still
become quiet or calm, especially after a state of agitation