An instrumented chair (IC) is proposed in this study to evaluate the sitting posture in a simple manner. This chair is capable of measuring the forces and pressure distribution during sitting in critical regions, i.e., under feet, sitting, and armrest regions, which are sensorized. One of the authors of this manuscript participated in these experiments. The results show that the difference in forces at the right and left side and also the pressure distribution at the hands and feet separately during sitting and standing using this relatively low-cost and accessible system.