# How to use the formula to calculate the Total Fertility Rate (TFR) and the Age Specific Fertility Rate (ASFR)

The Total Fertility Rate(TFR) is a fertility rate or birth rate used in demography to help understand the fertility experience and demographic processes of a particular population. The Total Fertility Rate (TFR) can be defined as "…the average number of children that would be born per woman if all women lived to the end of their childbearing years and bore children according to a given fertility rate at each age" (CIA World Factbook) It is one of the most used measurements to compare populations in demography. However, before you can calculate the Total Fertility Rate, you must calculate the Age Specific Fertility Rates (ASFR) for the women of childbearing years in a population.

Age Specific Fertility Rate (ASFR)

Typically, Age Specific Fertility Rates are done in 5 year age groups for women between the ages 15 - 49 or 18 - 49, depending on the available data and population. The formula for the Age Specific Fertility Rate is:

Age Specific Fertility Rate (ASFR) = (Number of births to women in age group i / Number of women in age group i) x 1000

Total Fertility Rate (TFR)

After calculating all of the Age Specific Fertility Rates for the population, you can move on to calculating the Total Fertility Rate. The formula for the Total Fertility Rate is:

Total Fertility Rate (TFR) = (The sum of the Age Specific Fertility Rates x The number of years in each age group) / 1000

The final number you arrive at is the Total Fertility Rate (TFR) for the studied population. A Total Fertility Rate of 2.1 is considered replacement fertility which means that the population is stable (although this is not the case in high mortality populations), above or below means that the population is growing or shrinking. Furthermore, it is important to understand that women of the studied population have not experienced nor necessarily will experience the Total Fertility Rate of any given year.

Foday Kamara on September 02, 2018:

very useful information but there is one thing left, the calculation or example of ASFR and TFR.

Arun gyawali on September 26, 2016:

very useful information for me..thank you

Bidyut on December 19, 2015:

Thank you, its easy to remember

Dina on August 25, 2015:

so simple and easy to understand

Abekebe on August 04, 2015:

Thanks! Very Supportive!

numan on April 09, 2015:

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isaiah hunuato hunis on March 10, 2015:

nice work. more grace to you

i really wish to be part

Clemmence on April 22, 2014:

man on March 04, 2014:

swornim adhikari on August 09, 2013:

that's very useful one

sudarsan raju k on July 29, 2013:

It is very useful

Heather Jacobs (author) on June 19, 2012:

Hi Giselle. Thank you very much! I'm glad you found it helpful!

Giselle Maine on June 19, 2012:

A helpful definition of how this number is actually derived. Thanks for this useful hub.