The wheal, produced by tuberculin skin tests, was identified by nurses through marking its edges. Four marks were made and measured – the greatest length of each mark to another mark was considered the size of the wheal. An attempt to imitate the procedure was done by designing a system that can measure the marked sides of the wheal. The implemented system used an algorithm that located the four marks in an image. These four marks were measured using the Euclidean distance to determine the distance between each other. Among the 6 edges of the four marks, the one with the greatest length was considered the size of the wheal. Using a scale with a defined size, the pixel value of the greatest length was converted in millimeters. The results showed that the system’s measurement was always less than the measurement of the nurse. With an accuracy of 91.53% for the test data, the researchers were able to implement a system that can facilitate in reading the results of tuberculin skin test.