In two similar geometric figures, the ratio of their corresponding sides is called the scale factor. To find the scale factor, locate two corresponding sides, one on each figure. Write the ratio of one length to the other to find the scale factor from one figure to the other. say a triangle had points of A(-1,0),B(0,1),and C(1,0) and the scale factor is two you basically double all the points so the A' is (-2,0), B' is (0,2), and C' is (2,0).