This research aims to design a sensor-based tool for checking bilateral leg muscle circumference balance in athletes. This study employs a Research and Development (R&D) design. This research involved 3 experts who were competent in their fields, namely an instrumentation physicist, a physiotherapist, and a sports physiologist, whose aim was at the validation test stage, to find out the weaknesses and strengths of the product that had been designed. After carrying out the validation test stage, the resulting product will be tested for use in the field. A total of 10 men who were selected using the Purposive Sampling technique with ages ranging from 20 to 28 years. The data obtained was tested using the r-correlation method. The main results of our research report that this sensor-based bilateral leg muscle circumference balance examination tool is valid, practical, effective, and reliable as a measuring tool for leg muscle circumference balance examination. This tool proves highly beneficial for healthcare professionals, particularly sports physiotherapists, by aiding in muscle balance assessments.