How to Calculate Total Fertility Rate Example

Total Fertility Rate (TFR) Calculator

Enter the Age-Specific Fertility Rate (ASFR) for each 5-year age cohort. ASFR is typically measured as the number of live births per 1,000 women in that specific age group.

Calculation Result:

TFR = 0.00 children per woman

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How to Calculate Total Fertility Rate: A Detailed Example

The Total Fertility Rate (TFR) is one of the most important demographic indicators. It represents the average number of children a woman would have if she survived to the end of her reproductive years and experienced the current age-specific fertility rates (ASFR) throughout her life.

The TFR Formula

When using 5-year age groups (the most common format for census data), the formula to calculate TFR is:

TFR = 5 × Σ(ASFR_i / 1,000)

Where:

• 5: The width of the age interval (15-19, 20-24, etc.).
• ASFR_i: The fertility rate for age group i, expressed per 1,000 women.
• Σ: The sum of the rates across all age groups (usually 15-49).

Realistic Example Calculation

Imagine a hypothetical country with the following fertility data per 1,000 women:

Age Group	ASFR (Births per 1,000 women)
15-19	10
20-24	70
25-29	110
30-34	95
35-39	50
40-44	15
45-49	2

Step 1: Sum the rates.
10 + 70 + 110 + 95 + 50 + 15 + 2 = 352

Step 2: Divide by 1,000 (to get the rate per woman).
352 / 1,000 = 0.352

Step 3: Multiply by the age group interval (5 years).
0.352 × 5 = 1.76

In this example, the Total Fertility Rate is 1.76 children per woman. Since this is below the "replacement level" of 2.1, the population may eventually decline without immigration.

Why 2.1 is Important

A TFR of roughly 2.1 is known as Replacement-Level Fertility. This is the average number of children per woman needed to keep the population size constant from one generation to the next, accounting for infant mortality and the fact that slightly more boys are born than girls.

function calculateTFR() { var a1519 = parseFloat(document.getElementById('asfr1519').value) || 0; var a2024 = parseFloat(document.getElementById('asfr2024').value) || 0; var a2529 = parseFloat(document.getElementById('asfr2529').value) || 0; var a3034 = parseFloat(document.getElementById('asfr3034').value) || 0; var a3539 = parseFloat(document.getElementById('asfr3539').value) || 0; var a4044 = parseFloat(document.getElementById('asfr4044').value) || 0; var a4549 = parseFloat(document.getElementById('asfr4549').value) || 0; var sumASFR = a1519 + a2024 + a2529 + a3034 + a3539 + a4044 + a4549; if (sumASFR === 0) { alert("Please enter at least one fertility rate value."); return; } // Formula: (Sum of ASFR / 1000) * 5 var tfr = (sumASFR / 1000) * 5; var resultArea = document.getElementById('tfr-result-area'); var resultVal = document.getElementById('tfr-value'); var interpretation = document.getElementById('tfr-interpretation'); resultVal.innerHTML = tfr.toFixed(2); resultArea.style.display = 'block'; var interpText = ""; if (tfr > 2.1) { interpText = "This rate is above the replacement level (2.1), indicating a growing population."; } else if (tfr 0) { interpText = "This rate is below the replacement level (2.1), which may lead to population decline over time."; } else if (tfr === 2.1) { interpText = "This rate is exactly at replacement level fertility."; } interpretation.innerHTML = interpText; // Scroll to result resultArea.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }