According to the Population Reference Bureau, Total Fertility Rate (TFR) is defined as, “the average number of children a women would have assuming that current age-specific birth rates remain constant throughout her childbearing years.” Simply put, total fertility rate is the average number of children a woman would have if a she survives all her childbearing (or reproductive) years. Childbearing years are considered age 15 to 49.

The total fertility rate can be calculated using age-specific birth rates. An age-specific birth rate is the number of babies born within a 5-year increment during reproductive years. The TFR is the calculation of adding up all the age-specific birth rates for a population and multiplying by five. (The sum is multiplied by five because the age-specific birth rates are in 5-year increments.) While the TFR gives a good picture of current fertility rates of a place or a population, the TFR won’t actually predict how many children a woman will have because it’s an average; different things will factor into this for different women – location, decisions to wait to have children, etc.

As with any average, one should keep in mind outliers, both very high and very low TFRs that influence the total average for a specific population. The current total fertility rate for the world is 2.5. Influencing this are countries that have TFRs of 6 and higher such as Niger (7.6), Democratic Republic of the Congo (6.3), and Uganda (6.2). But on the other end of the spectrum are countries such as the United Kingdom (2.0), Brazil (1.8), or Japan (1.4) that have lower total fertility rates, averaging 2 or below.

Check out the World Population Data Sheet to see total fertility rates around the world, by region and country.