One of the most fundamental problems in the field of geotechnical engineering is the prediction of bearing capacity and settlement of shallow foundations on cohesion-less soil subjected to vertical central loading. The fact is that commonly used SHAPE FACTORS in the current design practice for estimating the bearing capacity and modulus of subgrade reaction of a shallow foundation are partially empirical values proposed by (Terzaghi, 1943). On the other hand, the current design of shallow foundation on cohesionless soil does not take into consideration the scale effect between the soil particles and foundation geometry. This may result in an excessively conservative design, which in turn results in unnecessary costs of the foundation. Therefore, and to take into account the realistic effect of the three-dimensional mechanism of soil deformation for foundations with various aspect ratios B/L on the shape factor in the classical formulas and theories of ultimate bearing capacity of shallow foundation, a series of small-scale model foundation tests were carried out on a practical type of sand (Toyoura sand) and the three-dimensional mechanism of deformation has been closely monitored and recorded at the end of each performed test. This research presents the main observations and results of the square, rectangular and strip model tests with constant foundation base width B conducted on compacted sand. Finally, the results are presented and compared to those from literature and preliminary conclusions and recommendations are drawn.