calculation vs reckoning

calculation and reckoning both are nouns.

Word	Noun	Adjective	Verb	Adverb
calculation	Yes	No	No	No
reckoning	Yes	No	No	No

As nouns, calculation and reckoning are synonyms defined as:

calculation and reckoning: problem solving that involves numbers or quantities

Other synonyms of calculation include computation, figuring.

calculation (noun)	reckoning (noun)
the procedure of calculating; determining something by mathematical or logical methods	the act of counting; reciting numbers in ascending order
problem solving that involves numbers or quantities	problem solving that involves numbers or quantities
planning something carefully and intentionally	a bill for an amount due