estimation vs reckoning

estimation and reckoning both are nouns.

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

As nouns, reckoning is a hypernym of estimation; that is, reckoning is a word with a broader meaning than estimation:

Other hypernyms of estimation include calculation, computation, figuring.

estimation (noun)	reckoning (noun)
a judgment of the qualities of something or somebody	the act of counting; reciting numbers in ascending order
an approximate calculation of quantity or degree or worth	problem solving that involves numbers or quantities
the respect with which a person is held	a bill for an amount due
a document appraising the value of something (as for insurance or taxation)