low-cal vs calorie-free

low-cal and calorie-free both are adjectives.

Word	Noun	Adjective	Verb	Adverb
low-cal	No	Yes	No	No
calorie-free	No	Yes	No	No

As adjectives, low-cal and calorie-free are synonyms defined as:

Other synonyms of low-cal include light, lite.

low-cal (adjective)	calorie-free (adjective)
having relatively few calories	having relatively few calories