This paper presents an analytical method for one to compute the centroid of the overlapping area of two intersecting circles with arbitrary orientation. We also extend the solution to estimate the centroid of the overlapping area of three intersecting circles. Furthermore, based on the analytical solution of centroid computing, we propose a cell-based localization technique, namely Centroid Based Location (CBL) for wireless sensor networks. CBL works by finding the centroid of intersection of any two circles. In particular, we study the effect of power level mismatch among anchors. Simulation results show that CBL can significantly improve the accuracy while reducing the transmission power of anchors.