According to the 2015 Census, the age group with the highest population in Sitangkai is 5 to 9, with 4,806 individuals. Conversely, the age group with the lowest population is 80 and over, with 68 individuals.

Combining age groups together, those aged 14 and below, consisting of the young dependent population which include infants/babies, children and young adolescents/teenagers, make up an aggregate of 40.20% (13,400). Those aged 15 up to 64, roughly, the economically active population and actual or potential members of the work force, constitute a total of 57.82% (19,273). Finally, old dependent population consisting of the senior citizens, those aged 65 and over, total 1.98% (661) in all.

The computed Age Dependency Ratios mean that among the population of Sitangkai, there are 70 youth dependents to every 100 of the working age population; there are 3 aged/senior citizens to every 100 of the working population; and overall, there are 73 dependents (young and old-age) to every 100 of the working population.

The median age of 19 indicates that half of the entire population of Sitangkai are aged less than 19 and the other half are over the age of 19.