Meaning : An appraisal that is too high.
Synonyms : overappraisal, overestimation, overvaluation
Meaning : A calculation that results in an estimate that is too high.
Synonyms : overestimation, overrating, overreckoning
Meaning : Make too high an estimate of.
							Example : 
							He overestimated his own powers.
							
Synonyms : overrate
Make too low an estimate of.
He underestimated the work that went into the renovation.Meaning : Assign too high a value to.
							Example : 
							You are overestimating the value of your old car.
							
Synonyms : overvalue
Assign too low a value to.
Don't underestimate the value of this heirloom-you may sell it at a good price.