Project the future value of your recurring contributions over time.
Monthly
Quarterly
Yearly
Projections Summary
Total End Balance:
Total Contributions:
Total Yield Earned:
Understanding Periodic Deposit Calculations
A Periodic Deposit Rate Time Calculator is a specialized tool used to determine how recurring contributions grow when subjected to compound growth over a specific timeline. Unlike a simple savings projection, this formula accounts for the mathematical "snowball effect" where both your principal and your accumulated yields generate additional earnings.
The Core Components
Starting Balance: The initial lump sum you have at the beginning of the timeline.
Periodic Contribution: The fixed amount added to the balance at regular intervals (monthly, quarterly, or annually).
Growth Yield: The annual percentage rate at which the balance increases.
Duration: The total length of time the cycle continues, usually measured in years.
How the Math Works
The calculation uses the Future Value of an Ordinary Annuity formula combined with the compound growth of the starting principal. The formula is expressed as:
If you start with 1,000, contribute 200 per month for 10 years at an annual growth yield of 7%:
Your total contributions over 10 years would be 24,000 (plus the 1,000 start).
Due to compounding, your total balance would grow to approximately 36,410.
The total yield earned simply by letting the periodic deposits compound would be roughly 11,410.
This illustrates the importance of the Time variable in the Periodic Deposit equation. The longer the duration, the more the "yield on yield" dominates the total balance.
function calculatePeriodicGrowth() {
var p = parseFloat(document.getElementById('initialPrincipal').value);
var pmt = parseFloat(document.getElementById('periodicDeposit').value);
var r = parseFloat(document.getElementById('growthRate').value) / 100;
var t = parseFloat(document.getElementById('timeDuration').value);
var n = parseInt(document.getElementById('depositFrequency').value);
if (isNaN(p) || isNaN(pmt) || isNaN(r) || isNaN(t)) {
alert("Please enter valid numerical values for all fields.");
return;
}
var resultDiv = document.getElementById('periodicResult');
var totalBalanceElem = document.getElementById('totalBalance');
var totalContribElem = document.getElementById('totalContributions');
var totalGrowthElem = document.getElementById('totalGrowth');
var periods = n * t;
var ratePerPeriod = r / n;
var futureValue = 0;
if (ratePerPeriod === 0) {
futureValue = p + (pmt * periods);
} else {
// Principal Growth: P(1 + i)^n
var principalGrowth = p * Math.pow(1 + ratePerPeriod, periods);
// Annuity Growth: PMT * [((1 + i)^n – 1) / i]
var annuityGrowth = pmt * ((Math.pow(1 + ratePerPeriod, periods) – 1) / ratePerPeriod);
futureValue = principalGrowth + annuityGrowth;
}
var totalInvested = p + (pmt * periods);
var totalEarned = futureValue – totalInvested;
totalBalanceElem.innerHTML = futureValue.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
totalContribElem.innerHTML = totalInvested.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
totalGrowthElem.innerHTML = totalEarned.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
resultDiv.style.display = 'block';
}