overestimation vs overreckoning

overestimation and overreckoning both are nouns.

Word	Noun	Adjective	Verb	Adverb
overestimation	Yes	No	No	No
overreckoning	Yes	No	No	No

As nouns, overestimation and overreckoning are synonyms defined as:

overestimation and overreckoning: a calculation that results in an estimate that is too high

Other synonyms of overestimation include overestimate, overrating.

overestimation (noun)	overreckoning (noun)
a calculation that results in an estimate that is too high	a calculation that results in an estimate that is too high
an appraisal that is too high