A All companies in energy sector especially petroleum and gas industry in the process of drilling would definitely want to have the minimum and but stillsafe at its operation. Therefore, the planning of casing design must really becalculated. Step one in casing design is setting down the casings as retaining barrier of the wellbore and to maintain hole stability while the casings are connected from surface to sub-surface during drilling process and production process. Secondly in the casing design is determining the depth and the position at casing to be set and cemented, also we have to calculate all the pressures exerted on the casing string, such as burst pressure, collapse pressure, and tension pressure. Those three pressures affect the strength of casing at the time of installation as well as during the production process must be calculated as a reference to determine the size, grade, weight, and exerted type of connection casing used, so there will be a optimized calculation. This final project evaluates casing design of R1, Prabumulih, South Sumatera and optimizes casing grade. The evaluation focuses on casing setting depth and suitable casing grade selection that well result in optimum casing string in term of safety and economic. This study uses Maximum Load with 1/4 lost and 3/4 mud return assumption. I sincerely hope that this study can be used to evaluate the best casing design and safe.