The Forming Limit Diagram (FLD) is a criterion used to assess the formability of sheet metal during a manufacturing process. Traditionally, FLDs are obtained through manual measurements using Mylar tape or through the use of automatic deformation measurement systems such as ARMIS and ARGUS. However, the use of Mylar tape is not user-friendly and can result in errors. Additionally, the cost of using automatic measuring equipment is high. To address these challenges, we propose a method that utilizes a low-cost USB digital microscope and the Python-based open-source library, OpenCV, to obtain forming limit diagrams. This approach allows for the measurement of deformation on specimens by analyzing circles printed on them. To evaluate the performance of this method, a circular grid was printed on a sus430 0.3 t specimen and a nakajima test was conducted. The strain data obtained using this system was then compared to the FLD obtained with the ARGUS system. The results confirmed that the formability of sheet metal can be assessed at a lower cost using our proposed method.