Conventional stabilization (using cement, lime, etc.) of soft subgrades incurs high project costs and raises environmental concerns. An alternative stabilization technique that can benefit the pavement without compromising design criteria and pavement performance is the foremost instigating aspect for highway industries. Thus, in this study, the on-field existing effective California Bearing Ratio (CBR) equal to 10% was first simulated in the large-scale test chamber. The prepared unstabilized and stabilized pavement base with Polyethylene terephthalate (PET) biaxial geogrid (PET80) (the ultimate tensile strength equal to 80 kN/m in the machine and cross-machine direction) sections were loaded with a static linear hydraulic actuator having a loading capacity of 100 kN for quantifying the benefit. The benefit rendered by geogrid is quantified in terms of Modulus Improvement Factor (MIF), which is used in mechanistic-empirical pavement design guidelines to assess the pavement's overall performance and reduce the use of natural aggregate. The crucial design inputs of MIF value tested at large-scale laboratory level are further validated in the field through conducting static plate load test for the initial design traffic of 150 MSA (Million Standard Axles) and CBR = 10%. The test results indicated a marginal difference in MIF values observed from laboratory and field validation. The MIF values of PET80 reinforced pavement obtained through laboratory and field were 1.96 and 1.89, respectively. Thus, the benefit indicated that the laboratory obtained MIF value was 1.04 times higher than the field. The overall reduction in asphalt and base layer was 38% and 15%, respectively, for MIF value considered in the study.