overestimate

nouns

an appraisal that is too high
overappraisal, overestimate, overestimation, overvaluation
a calculation that results in an estimate that is too high
overestimate, overestimation, overrating, overreckoning

verbs

make too high an estimate of
"He overestimated his own powers"
overestimate, overrate
is derived from
overestimation
is derived from
overestimation
antonym
underestimate
assign too high a value to
"You are overestimating the value of your old car"
overestimate, overvalue
is derived from
overestimation
antonym
underestimate