overestimate

Plural: overestimates

Noun

• an appraisal that is too high
• a calculation that results in an estimate that is too high
• An estimate that is too high.

Verb

• make too high an estimate of
  • "He overestimated his own powers"
• assign too high a value to
• To judge or calculate too highly.

Examples

• I overestimated the number of attendees, and bought far too much food for the party.

Synonyms

overappraisal, overestimation, overrate, overrating, overreckoning, overvaluation, overvalue

Antonyms

underestimate, undervalue