Use this fertility measure when the births, women at risk, parity categories, and observation period follow the definition required by the selected method.

ASFR

Age-specific fertility rates of the cohort, per woman per year.

Class width

Width of each age class in years.

CFF

Children born per woman by the end of the reproductive period.

Period and cohort fertility answer different questions. Survey recall, parity truncation, changing age patterns, union definitions, and mismatched exposure populations can materially change the result.

Pair period fertility with cohort measures, parity distributions, or wanted-fertility indicators when available. These complementary views separate timing changes from completed family size and stated preferences.

• Replacement Fertility With Mortality Checker

  Compute the replacement total fertility rate as the reciprocal of the product of the female birth share and female survival to the reproductive ages, then classify an observed TFR against it within a stated tolerance.

• Wanted Versus Actual Fertility Gap

  Compute the gap between observed total fertility and the wanted total fertility reported in survey style questions, together with the share of observed fertility that exceeds wanted fertility.

• Birth Interval Median By Parity Calculator

  Compute the median length of birth intervals in months for a set of closed intervals observed at a given parity transition.