In this study, the most important models for estimating the volume of grout injected into the rock are introduced and then evaluated using real results in the Seimare and Talwar dams. These models are developed based on engineering and geotechnical geological conditions and hydraulic characteristics of discontinuities, as well as injection pressure and grout properties. The present study shows that the fourth model, compared to other models, provides a better estimate and has the lowest error (28% in Seimare dam and 38% in Talwar dam), and the use of this model in estimating grout in other construction sites is recommended. The first model has the highest error (75% in the Seimare dam and 98% in the Talwar dam). The second, third, and fifth models in the Seymareh Dam show error values ​​of 57%, 56%, and 49%, respectively, and in the Talwar Dam, error values ​​of 69%, 68%, and 73%. In general, the relative error of injection modeling in the Seimare Dam is less than in the Talwar Dam. This is because, at the Talwar construction site, due to the lower quality of the rock mass and numerous joints, more complex conditions prevail. Analytical models cannot consider all parameters, resulting in a greater difference between the actual and calculated corrosion values. Consequently, a greater error is created compared to the Seymareh construction site.