Planning for your golden years requires understanding the power of compound interest and consistent contributions. This calculator helps you estimate the future value of your retirement account based on your current age, your target retirement date, and your investment habits.
Understanding the Inputs
Current Age & Retirement Age: This determines your time horizon. The longer you have until retirement, the more time your money has to grow exponentially.
Current Savings: The lump sum you already have invested in accounts like a 401(k), IRA, or brokerage account.
Monthly Contribution: The amount you plan to add to your savings every month. Consistency is often more important than the initial amount.
Expected Annual Return: The average yearly profit from your investments. Historically, the stock market averages around 7-10% before inflation.
Inflation Rate: This accounts for the rising cost of living, showing you what your future money might actually feel like in "today's dollars."
Realistic Example:
Meet Sarah, a 25-year-old starting her career. She has $5,000 in her 401(k). She decides to contribute $400 every month. If she retires at 65 and earns an average 8% annual return, her nest egg could grow to approximately $1.41 Million. However, if she waits until age 35 to start that same $400 monthly contribution, her final balance drops to roughly $610,000. This illustrates the "Cost of Delay."
Why Inflation Matters
A million dollars today will not buy the same amount of goods 30 years from now. By including an inflation rate (typically 2-3%), the calculator provides an "Inflation-Adjusted" figure. This helps you understand the purchasing power of your future savings, allowing for a more accurate lifestyle projection.
function calculateRetirement() {
var currentAge = parseFloat(document.getElementById('currentAge').value);
var retireAge = parseFloat(document.getElementById('retireAge').value);
var currentSavings = parseFloat(document.getElementById('currentSavings').value);
var monthlyContribution = parseFloat(document.getElementById('monthlyContribution').value);
var annualReturn = parseFloat(document.getElementById('annualReturn').value) / 100;
var inflationRate = parseFloat(document.getElementById('inflationRate').value) / 100;
if (isNaN(currentAge) || isNaN(retireAge) || isNaN(currentSavings) || isNaN(monthlyContribution) || isNaN(annualReturn)) {
alert("Please enter valid numeric values in all fields.");
return;
}
if (currentAge >= retireAge) {
alert("Retirement age must be greater than current age.");
return;
}
var yearsToGrow = retireAge – currentAge;
var monthsToGrow = yearsToGrow * 12;
var monthlyRate = annualReturn / 12;
// Future Value of Current Savings: FV = P(1 + r)^n
var fvCurrent = currentSavings * Math.pow((1 + monthlyRate), monthsToGrow);
// Future Value of Monthly Contributions: FV = PMT * [((1 + r)^n – 1) / r]
var fvMonthly = 0;
if (monthlyRate > 0) {
fvMonthly = monthlyContribution * ((Math.pow((1 + monthlyRate), monthsToGrow) – 1) / monthlyRate);
} else {
fvMonthly = monthlyContribution * monthsToGrow;
}
var totalBalance = fvCurrent + fvMonthly;
// Inflation Adjusted Value: Adjusted = Total / (1 + i)^n
var adjustedBalance = totalBalance / Math.pow((1 + inflationRate), yearsToGrow);
document.getElementById('result').style.display = 'block';
document.getElementById('totalValue').innerHTML = '$' + totalBalance.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('inflationAdjusted').innerHTML = 'In today\'s purchasing power (adjusted for ' + (inflationRate * 100).toFixed(1) + '% inflation), this is equivalent to: $' + adjustedBalance.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + '';
document.getElementById('result').scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}