simmer down vs calm down

simmer down and calm down both are verbs.

Word	Noun	Adjective	Verb	Adverb
simmer down	No	No	Yes	No
calm down	No	No	Yes	No

As verbs, simmer down and calm down are synonyms defined as:

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

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

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