Over-excavation and replacement are the most commonly used ground modification techniques for shallow foundations. In soft soils, however, the extent of replacement by relatively larger (up to 19 mm) granular material was unknown. A total of 97 tests, consisting of 10 small and 87 numerical model tests, were carried out on two types of foundations, namely strip, and square. The width W and the depth of the replaced zone H were varied in each test and the ultimate bearing capacity q u was calculated. The experimental and numerical analyses were compared by computing q u from two methods (tangent intersection method (TIM) and 0.1B method). The improvement in q u was plotted as the dimensionless factor bearing capacity ratio (BCR) vs. depth ratio H/B for each foundation. A significant increase in BCR was observed from H/B of 1.5 to 4 for strip foundation and 2.5 to 3 for a square foundation. There was an insignificant increase in BCR after H/B of 4 and 3 for strip and square foundations, respectively. The width of the replacement was recommended as 2B for square foundations, while no value was suggested for strip foundation owing to a steady increase in the BCR. In addition, it has been observed that the depth of replacement is a major component in improving the bearing capacity compared to the width of replacement.