overestimate
o-ver-es-ti-mate
noun
An estimate that is too high or too favourable.
"The initial figure was an overestimate."
verb
To judge something as greater than its true worth, size, or importance.
"Don't overestimate his abilities."
Thesaurus
Synonyms: overvalue, overappraisal, overvaluation, overestimation, overrate, overreckoning, overrating
Antonyms: underestimate, underrate, undervalue