estimate
(verb)

If you estimate a quantity or value, you make an approximate judgment or calculation of it.*
 The lawyer tried to estimate his fee but would only be able to give the exact amount after he counted the hours he worked.

estimate
(noun)

An estimate is an approximate calculation of a quantity or value.
 Before the trial, the lawyer gave the client an estimate of his fee. By the end of the trial the figure was 5 times larger than the original estimate.

