Determining open pit limit is a very important step in open pit development design, which can save cost and provide maximum economic benefit. When the critical depth and the outline for open pit mining are properly determined with mining and geological conditions using the suitable optimization approaches, we can reduce the volume of the overburden (waste) material and normalize the production at a higher level. In this paper, we suggest a method to determine the ultimate pit limit (UPL) by comprehensively considering the mining geological characteristics of target orebody and the economic value of mining block, in contradistinction to the conventional method for setting open pit limit on the principle that the contour stripping coefficient should not be greater than the economically reasonable stripping ratio (i.e., limit stripping ratio). First, we convert 3D block model into a value block model and construct the function for value attribute computation on each block using Surpac software. Then, we propose a combined procedure of the floating cone method and the Lerchs–Grossman (LG) algorithm in order to set the UPL. Consequently, the applicability of the proposed method is verified through a case study for a gold mine.