With the continuous improvement of the calculation speed of computer, tool positioning methods based on numerical calculation in five-axis NC programming will play a greater role. First, this paper introduces three numerical methods for calculating tool position error distribution between a torus cutter and design surface in 5-axis machining of sculptured surfaces, namely a method for discretizing design surface, a method for discretizing the torus central circle, and a longitude method. At the same time, the detailed calculating steps are also given. An example of a cylindrical surface machined with torus tool is then conducted to compare and analyze the calculation accuracy and efficiency of the above methods. Results obtained show that the calculating deviation for computing tool position error distribution using the method for discretizing the torus central circle is minimum, while that using another two methods are larger; the calculation time of the method for discretizing the torus central circle is shortest, while that of the longitude method is longest; within the given programming tolerance, the machining strip widths calculated by the above methods are appropriately same, and the maximum deviation of actual machining strip width is within 2% of the theoretical value.