Lake Pandan is one of the lakes located in Tapanuli Tengah district. Morphometry can explain the biological and chemical processes of the lake, regulate nutrient load, productivity and the influence of input loads from the surrounding area. Therefore, the morphometry of lake was needed as a basis for lake utilization and management. This is what underlies the morphometric research of Lake Pandan, where there has been no research on this topic. The purpose of this study was to determine the morphometry of Lake Pandan. This research was conducted on April 2019. The results of measurements of lake surface dimensions obtained that Lake Pandan has an area of ± 103 Ha with a maximum length of 2,034.60 m, a maximum width of 1,033.38 m, and a length of around the lake of 5,395 m. With an edge (Sl) of 5.395 m so that the Lake Development Index (LDI) was obtained at 0.302. The LDI value of 0.302 illustrates that the lake has an irregular shape. LDI can be used to describe the level of productivity of water if the value is greater, the waters are more fertile. The subsurface dimension found that the average depth (Z) of Lake Pandan was 0.21 m with maximum depth (Zmax) 1.7 m. The morphometric parameters of lake influence the physical, chemical and biological processes in the waters of Lake Pandan, such as depth. Based on depth, Lake Pandan has low stability and easy to experience stirring.