function calculateGARetention() {
// Get input values
var startUsers = parseFloat(document.getElementById("ga_start_users").value);
var endUsers = parseFloat(document.getElementById("ga_end_users").value);
var newUsers = parseFloat(document.getElementById("ga_new_users").value);
// Validation
if (isNaN(startUsers) || isNaN(endUsers) || isNaN(newUsers)) {
alert("Please enter valid numbers for all fields.");
return;
}
if (startUsers endUsers) {
alert("New Users cannot exceed Total Users at the end of the period.");
return;
}
// Calculation Logic: ((E – N) / S) * 100
var retainedUsers = endUsers – newUsers;
var retentionRate = (retainedUsers / startUsers) * 100;
var churnRate = 100 – retentionRate;
// Display Results
document.getElementById("ga_results").style.display = "block";
// Format Retention Rate
var retDisplay = document.getElementById("result_retention_rate");
retDisplay.innerHTML = retentionRate.toFixed(2) + "%";
// Color coding for retention
if (retentionRate >= 80) {
retDisplay.className = "result-value high-score";
} else if (retentionRate 100) {
feedback.innerHTML = "Note: A rate over 100% indicates users who were inactive at the start returned during this period (resurrected users).";
} else if (retentionRate < 0) {
feedback.innerHTML = "Note: Negative retention suggests data discrepancies between New Users and Total End Users.";
} else {
feedback.innerHTML = "This metric represents the percentage of existing users who remained active during the period.";
}
}
How to Calculate Retention Rate in Google Analytics
Understanding user retention is pivotal for assessing the long-term health of a website or application. While Google Analytics 4 (GA4) provides built-in cohort analysis and retention reports, understanding the manual calculation behind these metrics allows analysts to audit their data and calculate retention across custom timeframes that may not be available in standard reports.
The User Retention Formula
The standard formula used to calculate user retention rate over a specific period is known as the Customer Retention Rate (CRR) formula. In the context of Google Analytics, we substitute "Customers" with "Users" or "Visitors".
Retention Rate = ((E – N) / S) × 100
Where:
E (End Users): The total number of active users recorded at the end of the time period.
N (New Users): The number of new users acquired during that specific time period.
S (Start Users): The total number of active users recorded at the start of the time period.
Step-by-Step Calculation Guide
To perform this calculation using data from Google Analytics, follow these steps:
Define Your Period: Choose a timeframe (e.g., Monthly, Quarterly).
Identify Start Users (S): Look at your "Total Users" count at the very beginning of the period.
Identify End Users (E): Look at your "Total Users" count at the very end of the period.
Identify New Users (N): Use the "New Users" metric in GA4 to see how many visitors were acquired strictly within that period.
Input Data: Enter these three figures into the calculator above to determine the percentage of users you retained.
Interpreting the Results
Retention Rate: This percentage tells you what portion of your user base stuck around. A high retention rate implies your content or product is sticky and valuable. In SaaS and apps, a retention rate above 35% for an 8-week period is often considered good, though this varies heavily by industry.
Churn Rate: This is the inverse of retention. If your retention rate is 70%, your churn rate is 30%. This represents the percentage of users who stopped visiting or using your site during the period.
Why GA4 Cohort Analysis Matters
While the formula above gives a snapshot of retention for a fixed period, Google Analytics 4 offers "Cohort Exploration." This tracks a specific group of users (a cohort) who shared a common characteristic (usually acquisition date) and visualizes how their retention drops off over time (Day 1, Day 7, Day 30). The calculator above is best used for high-level aggregate reporting when you need to report a single "Retention Score" for a month or quarter to stakeholders.