The design of this light refractive index practicum tool aims to design and make developments from existing tools. This research uses the Borg and Gall method, which is limited to the initial development stage. In the first stage, researchers made field observations about this practicum tool and conducted literature studies to find references for tool design, namely determining materials. The second stage determines the components of the tool and makes a design in the form of a 3-dimensional image to determine the scale of the tool size. Furthermore, the third stage is the development of researchers realizing the design in the form of tool drawings into prototypes for laboratory scale trials and revising if there is still unstable data. After the data generated is stable, the tool is made according to the design with a size that matches the practicum tool until it is ready for a limited trial. The limitation of this research is because it is still in the laboratory scale trial stage to see the stability and accuracy of the data results on the tool.