In calculating Dependency Ratio, the numerator is expressed as -
Dependency ratio 

The proportion of persons above 65 years of age and children below 15 years of age are considered to be dependent on the economically productive age group (15-64 years).
The ratio of combined age group 0-14 years plus 65 years and above to the 15-65 years age group is known as total dependency ratio.

Total dependency ratio = Age group 0-14 yrs & age group above 65 yrs / Age group between 15-65 yrs

It is also referred to as the societal dependency ratio and reflects the need for a society to provide for their younger and older population groups.