Enter the number of live births and female population for each 5-year age group.
Age Group
Live Births
Female Population
15-19
20-24
25-29
30-34
35-39
40-44
45-49
Calculation Result
Total Fertility Rate:
0.00
children per woman
How Is the Total Fertility Rate Calculated?
The Total Fertility Rate (TFR) is a standard demographic indicator used to estimate the average number of children a hypothetical cohort of women would have at the end of their reproductive period if they were subject during their whole lives to the fertility rates of a given period and if they were not subject to mortality.
The Mathematical Formula
The calculation involves summing the Age-Specific Fertility Rates (ASFR) for each 5-year age group and multiplying by the interval of the age group (usually 5).
TFR = 5 × ∑ (ASFR)
Where:
ASFR = (Live Births in Age Group) ÷ (Female Population in Age Group)
Step-by-Step Calculation Process
Data Collection: Gather data on the number of live births and the total female population for standard 5-year age groups (15-19 through 45-49).
Calculate ASFR: For each age group, divide the number of births by the female population. This gives you the Age-Specific Fertility Rate.
Summation: Add all the ASFR values together.
Interval Adjustment: Multiply the sum by 5 (since each group represents a 5-year span).
Interpreting the Result
Replacement Level (2.1): A TFR of approximately 2.1 is considered the "replacement level." This is the rate required for a population to replace itself from one generation to the next, accounting for mortality.
Below 2.1: Indicates a population that may shrink over time without immigration (e.g., Japan, South Korea, parts of Europe).
Above 2.1: Indicates a growing population (e.g., many countries in Sub-Saharan Africa).
Why is TFR Important?
Governments and economists use TFR to plan for future infrastructure needs. A high TFR might indicate a need for more schools and pediatric healthcare, while a low TFR might suggest a future labor shortage and increased strain on pension systems as the population ages.
function calculateTFR() {
// Define age groups for iteration
var ageGroups = [
{ id: '15_19′, label: '15-19′ },
{ id: '20_24′, label: '20-24′ },
{ id: '25_29′, label: '25-29′ },
{ id: '30_34′, label: '30-34′ },
{ id: '35_39′, label: '35-39′ },
{ id: '40_44′, label: '40-44′ },
{ id: '45_49′, label: '45-49′ }
];
var totalASFR = 0;
var breakdownHtml = "Age-Specific Fertility Rates (ASFR):";
var hasError = false;
// Iterate through inputs to calculate ASFR for each group
for (var i = 0; i 0 && population 0) {
asfr = births / population;
}
totalASFR += asfr;
// Format ASFR for display (per 1,000 women is standard for display, but calc uses decimal)
var asfrDisplay = (asfr * 1000).toFixed(1);
breakdownHtml += group.label + ": " + asfr.toFixed(4) + " (" + asfrDisplay + " births per 1,000 women)";
}
if (hasError) return;
// TFR = 5 * sum(ASFR) because the age intervals are 5 years
var tfr = totalASFR * 5;
// Display results
document.getElementById('tfr-value').innerHTML = tfr.toFixed(2);
document.getElementById('breakdown').innerHTML = breakdownHtml;
document.getElementById('result').style.display = 'block';
}