The work objective is to evaluate how the geometric transformations of the trailing edge of some airfoils affect the aerodynamic characteristics. Such transformations as the trailing edge thickening and rounding are considered. The performance of Wortmann FX 63-137, NACA 23024 и Clark Y is calculated. The effect of the trailing edge changes on their aerodynamic performance at Reynolds numbers from 200,000 to 1,000,000 is assessed. It is shown that the thickening of the trailing edge increases the drag coefficient up to some Reynolds number dependent on the airfoil, and thereafter it reduces. At that the increase of the lift coefficient is observed. The rounding of the trailing edge reduces both the lift and drag forces, and it can lead to the improvement of the airfoil lift-to-drag ratio for certain angles of attack. The data obtained can be used in the manufacture of blades with the profiles discussed.