A study conducted by the National Centre for Statistics and Information (NCSI) about the population projections in the Sultanate (2015 – 2040) expected that the number of Omanis will reach 4 million persons by 2040 according to the high-fertility assumption; compared to 3.8 million persons according to the medium-fertility assumption and 3.6 million persons according to the low-fertility assumption. The study indicated that the number of Omani population will increase with 2.4 million persons by the year 2040. The the number of Omani males will increase with 69% compared to about a 72% increase among the females according to average fertility assumption in the year 2040. According to the high fertility assumption, the percentage of Omani children under 15 years to the total number of the Omani population is expected to reach 30% in 2040 compared to about 25% according to the low fertility assumption. The percentage of children under 5 years to the total Omani population is projected to reach 11% according to the high fertility assumption; compared to about 8% according to the low fertility assumption. It is also projected that the Omani youth (15 – 29 years) will constitute about 27% of the total Omanis with about 3% decrease compared to the same value of the index recorded in the middle of 2015. The study projected that the number of Omani population in the working age (15 till 64 years) will reach 64% according to the high fertility assumption; which increases to 69% in the low fertility assumption. It is also expected that the Omani females of childbearing age will constitute 45% of the total Omani feamles in 2040 according to the medium fertility assumption. The study indicates that the dependency rate will reach 56 dependent persons per every 100 persons in the working age in the year 2040 according to the high fertility assumption; while it decreases to 45 dependent persons according to the low fertility assumption. As for the population indices at the governorates level, the study says that the largest projected increase in the number of population during the next twenty five years will be recorded in Muscat governorate where the projected increase reaches 322 thousand people on the assumption that the policy of decreasing the number of expatriates will continue. However; the size of the youth and young people category (less than 30 years) will decrease at Muscat governorate with 13% by 2040. In contrast, the lowest projected increase in the population is expected to be recorded in the middle of 2040 in Musandam governorate with an increase of 17 thousand people only. Muscat and Al-Batinah North Governorates will assimilate 41% of the total number of Omani Youth in the age group from (15 till 29 years); while two third of the Omani children under 5 years (constituting 66%) will be residing in Muscat, Al-Batinah South, Al-Batinah North and Al-Sharqiyah North Governorates. Generally speaking, in light of the three assumptions about the Omani populations' total fertility rates; which assume that the total fertility rate will decrease during the projection period; it appears that the populations increase in the three assumpations. This is called the Population Momentum; which is the driving force of the popultion growth. This means that the population growth will continue under the decrease according to the fertility rates. The study explains also that the population pyramid of the Omanis during the projection period moves closer towards achieving the demographic window by the year 2040. It is the stage in which the community reaches in the peak as for the size of population in the working age compared to the lowest percentage of dependent population (children and old persons). It is worth noting that the population projections that have been prepared were based on the base year with regard to the Omani population. As for the expatriate populations, they were based on the Royal Oman Police's data. Concerning the births and deaths data, the Ministry of Health's data were utilized. The process of projecting the population size, their properties and their growth trends during a specific period of time in a specific region is scientific and practical basis on which the planning and policy making operations are made. This projection or prediction is set using many scientific methods based on very accurate population data including the population data inputs during the specific projection period.