calorie-free vs low-cal

calorie-free and low-cal both are adjectives.

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

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

Other synonyms of calorie-free include light, lite.

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