PT Gunung Bara utama as the holder of Mining Business License Production Operations has conducted Some exploitation activities in the area of Mining Business License, with an area of Exploitation Mining Business License of 5.300 Ha. Furthermore, the company will open a new pit in the area where there is still coal distribution in the mining business license area, namely in Block A of PT Gunung Bara utama, therefore modeling activities, reserve calculations and mining designs are required so that a scheduled mining design will be produced and will be used in the next mine planning. Therefore, the determination of mining boundaries and the calculation of reserves is necessary to know the economic value of the Mine. The method used in this study is a block model method to determine the optimal potential area for mining activities, from the block model made solid batter block (with the contour of the structure as the lower limit and topography as the upper limit) and the triangle method to calculate the mined coal reserves. From the calculation of solid batterblock can be made resgraph based on the stripping ratio value of 10.5:1 from the resgraph result obtained different stripping ratio values and colored with certain colors, so that it can be determined the potential area for mining. The results of the research that has been done are obtained modeling coal deposits seam S01, S02, S03 and S04 have a thickness of seam, seam S01 2.75 meters, S02 20.7 meters, S03 2.64 and S04 2.74 meters. With the calculation of the estimated reserves of all seam in Pit Lom obtained coal amounted to 12,759,228.50 MT, overburden of 128,479,749.60 bcm, so obtained stripping ratio of 10.07:1, with a pit area of 216.02 hectares. Then in the design of disposal with the volume of overburden material that must be moved is 29,730,214.06 ccm. Disposal locations divided by 3 location points namely D1, D2, D3, the volume of each disposal is D1 16,098,371.91 ccm, D2 8,937,051.05 ccm, D3 4,960,990.8ccm. The total disposal volume is 29,996,413.80 ccm therefore the disposal design can meet the target of the total overburden volume that needs to be stockpiled. Keywords: Coal, Reserve Estimation, Stripping Ratio, Batter block Solid, Triangle Method.