【Estimation】 , 【estimate】 both mean the act of valuing or appraising, but they are rarely interchangeable.
In general, 【estimation】 implies the manner or measure in which a person or thing is valued or esteemed. Often the term comes close to personalopinion or pointofview, especially in respect to a thing′s value.
In general, 【estimate】 applies to the result of an appraisal or an evaluation (as of a thing′s worth, its cost, its size, or its prospects). It may connote an approximation to the truth that has been reached either by guessing or conjecture or as the outcome of careful consideration, expert knowledge, or profound study.
In a technical sense 【estimate】 implies the sum for which a piece of work (as the erection or repair of a building) can or will be undertaken.