In this paper, a ratio type estimator for population mean based on simple random sampling (SRS) and ranked set sampling (RSS) has been proposed. The expressions for mean square errors and its minimum values have been obtained. The proposed estimator under SRS design has been shown to be more efficient than the existing estimators. It has also been shown that proposed estimator under RSS design is always better than that under SRS design. Further, the proposed estimator has been shown to be better than the estimators proposed by Jemain et al [1] and Al-Omari et al [2]. A simulation study is performed to verify results of the proposed estimators.