overestimate

Noun

• a calculation that results in an estimate that is too high

• an appraisal that is too high

Verb

• assign too high a value to
  • You are overestimating the value of your old car
    

• make too high an estimate of
  • He overestimated his own powers
    

Related words

• Synonyms: 
  overestimation , overrating , overreckoning , overvaluation , overappraisal , overvalue , overrate
• Antonyms: 
  undervalue , underestimate , underrate