In this paper, simple approximate methods have been given to calculate the true value of an area on a Mercator chart. The introduction touches on the general characteristics of Mercator projection, and the area deformation on this projection is studied. As is known, in this conformal projection area deformations increase with the latitude and differentiate according to the location of the region. Therefore, the areas calculated or measured directly on these commonly used charts are not the true values. First, these two approximate methods-of which area values very close to the true values can be obtained-are introduced. Then, these methods have been applied to the regions located at low, middle, and high latitudes. In the conclusion, calculated areas have been compared with the true areas, closeness of the results have been examined, and the validity of the methods has been proved.