Image processing and mathematical reasoning are two powerful techniques to solve some of the complex problems. Since the perimeter of ellipse is not determined accurately as well as the existing perimeter equations are too complex, researchers attempt to find proper solutions for this issue. This paper proposes a novel approach to measure the perimeter of an ellipse by using image processing and mathematical reasoning. This approach consists of two stages. In the first stage, value of a pixel is calculated via a pixel-by-pixel image processing based on the perimeter of several circles having different radii. In the second stage, the perimeter of an ellipse is defined by the pixels of various ellipses having different diameters and the value of a pixel through a mathematical reasoning. Simulation results show that P = 1.14167p (a + b) is the suggested perimeter of an ellipse according to the considered simulation scenarios.