'Replacement level of a population is based on the calculation of :

(1) Sex-ratio

(2) Death rates

(3) Total fertility rates

(4) Birth rates

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The rate of natural increase or the growth rate of population refers to the difference between the birth rate and the death rate. When this difference is zero (or, in practice, very small) then we say that the population has ‘stabilised’, or has reached the ‘replacement level’, which is the rate of growth required for new generations to replace the older ones that are dying out. “Replacement level fertility” is the total fertility rate—the average number of children born per woman—at which a population exactly replaces itself from one generation to the next, without migration.