The construction of new highways and expressways is growing exponentially, increasing the demand for pavement materials. Aggregates are the primary natural materials used in the base and subbase courses. The limited and non-availability of superior quality aggregates pose concerns about importing material from far-off places, ultimately increasing construction costs and construction time. Geosynthetic materials like geogrids in the base/subbase courses in pavements are cost-effective and will reduce the demand for natural aggregates. The current study uses large-scale experiments to assert the modulus improvement factor (MIF) of a multilayered geogrid reinforced pavement system. A geogrid is positioned at the interface of the subgrade–subbase layer, and another is at the interface of the subbase–base layer. The MIF of a multilayer geogrid reinforced pavement system was assessed using two different methods. The applicability of both methods was discussed, along with an as-built pavement design example. The MIF values from both methods were calculated as 1.6 and 2.0.