well-off vs well-to-do

well-off and well-to-do both are adjectives.

Word	Noun	Adjective	Verb	Adverb
well-off	No	Yes	No	No
well-to-do	No	Yes	No	No

As adjectives, well-off and well-to-do are synonyms defined as:

well-off and well-to-do: in fortunate circumstances financially; moderately rich

Other synonyms of well-off include comfortable, easy, prosperous, well-fixed, well-heeled, well-situated.

well-off (adjective)	well-to-do (adjective)
fortunately situated	in fortunate circumstances financially; moderately rich
in fortunate circumstances financially; moderately rich