The statistical mixture design (SMD) method was used to find the optimum blending proportions of economical green cement by blending portland cement with fly ash, silica fume, and calcium carbonate. Twenty blends with different combinations of materials were tested on mortar mixtures to find the optimum and to analyze each. A graphical method was suggested for examining the mixture components on the response variables that included setting time and compressive strengths at 2, 7, and 28 days. The desirability function approach was used to calculate desired optimum blend of eco-cement at a minimum cost. The results from the experimental study were compared with the real-life situation of portland cement and pozzolanic portland cement analyzing on scanning electron microscope (SEM) for the microstructure. In mixture optimization, the SMD method is a useful tool to obtain a scientific solution instead of trial-and-error method with cost-effective mixture proportions.