The soil utilized as underneath the layer of sub-base in many civil engineering applications such as; roads, foundations of buildings, walkways, airfield, etc. The thickness of sub-base layer depends on the design load, project type and the soil type. Which will effect on the field density. This study was applied on a sub-base soil grade B as classified according to AASHTO which a wide spread in Iraq. Different tests were conducted on this soil to evaluate its properties such as sieve analysis, Atterberg's limits, compaction and chemicals. Three energies of compactive efforts were used in the laboratory work (EN1= 585.17 kJ/m3, EN2 =5898.5 kJ/m3, and EN3=1799 kJ/m3, ) to study the effect of different compactive efforts on the maximum dry density. Furthermore, built field model with the compactive effort of 1711.3kJ/m3 was used to determine the compaction ratio (RC). This model was 3m*1m * 0.80m which was from the confining base and sides by plain concrete to prevent the energy from transmitting to the soil behind and below the model. Four layer thicknesses (0.1m, 0.15m, 0.2m, and 0.3m) were used to study the effect of compactive effort on the layer thickness and then to evaluate the RC. The results obtained from this study showed that RC was Inversely proportional to the thickness of layer when it was equal or less than 0.2m. RC was (97%, 94.2% and 88.5%) at 0.1m, 0.15m, and 0.2m respectively. However, this was not the case when the layer thickness exceeded 0.2m. The results also showed that the adequate thickness was less than 0.2m.