Understanding compounding and small differences in growth rates.
Whether you are analyzing investment returns, projecting business user acquisition, estimating population changes, or tracking bacterial growth in a petri dish, understanding how different growth rates affect future outcomes over time is crucial.
This calculator uses the compound growth formula: Final Value = Initial Value × (1 + Rate)Time. It allows you to side-by-side compare two different scenarios (Scenario A and Scenario B) to visualize how even a small percentage difference in annual or period growth rate can lead to massive discrepancies over a long time horizon.
For example, starting with 10,000 units in two different scenarios—one growing at 6% and another at 8%—might seem like a small difference initially. However, over 20 periods, the 8% scenario will result in significantly higher total growth due to the power of compounding.
function calculateGrowthComparison() {
// 1. Get input values
var initAStr = document.getElementById("initA").value;
var rateAStr = document.getElementById("rateA").value;
var initBStr = document.getElementById("initB").value;
var rateBStr = document.getElementById("rateB").value;
var timeStr = document.getElementById("timePeriod").value;
// 2. Parse numerical values
var initA = parseFloat(initAStr);
var rateA = parseFloat(rateAStr);
var initB = parseFloat(initBStr);
var rateB = parseFloat(rateBStr);
var time = parseFloat(timeStr);
var resultDiv = document.getElementById("growthResult");
// 3. Validation: Ensure all inputs are valid numbers and non-negative where appropriate
if (isNaN(initA) || isNaN(rateA) || isNaN(initB) || isNaN(rateB) || isNaN(time) || time finalValueB) {
winnerText = "Scenario A grew larger.";
winnerClass = "color: #3498db;";
} else if (finalValueB > finalValueA) {
winnerText = "Scenario B grew larger.";
winnerClass = "color: #27ae60;";
} else {
winnerText = "Both scenarios ended with the same value.";
winnerClass = "color: #7f8c8d;";
}
// 6. Format Output
// Helper function to format numbers with commas
function formatNumber(num) {
return num.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ",");
}
var outputHTML = "
";
outputHTML += "
";
outputHTML += "Final Value A";
outputHTML += "" + formatNumber(finalValueA) + "";
outputHTML += "(Started at " + formatNumber(initA) + " with " + rateA + "% rate)";
outputHTML += "
";
outputHTML += "
";
outputHTML += "Final Value B";
outputHTML += "" + formatNumber(finalValueB) + "";
outputHTML += "(Started at " + formatNumber(initB) + " with " + rateB + "% rate)";
outputHTML += "
";
outputHTML += "
";
// 7. Display Result
resultDiv.style.display = "block";
resultDiv.innerHTML = outputHTML;
}