Investment Growth Calculator: Compound Interest Over Time

ANA›Life Services Authority›National Calculator Authority›Investment Growth Calculator: Compound Interest Over Time

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Investment Growth Calculator: Compound Interest Over Time

Calculate how your investment grows over time using compound interest, with optional regular contributions.

Initial Investment ($)

Regular Contribution ($)

Contribution Frequency

Monthly Quarterly Semi-Annually Annually

Annual Interest Rate (%)

Compounding Frequency

Monthly Quarterly Semi-Annually Annually Daily

Investment Period (Years)

Calculate

function invCalc() { var principal = parseFloat(document.getElementById('inv-principal').value); var contribution = parseFloat(document.getElementById('inv-contribution').value) || 0; var contribFreq = parseInt(document.getElementById('inv-contrib-freq').value); var annualRate = parseFloat(document.getElementById('inv-rate').value); var compoundFreq = parseInt(document.getElementById('inv-compound-freq').value); var years = parseFloat(document.getElementById('inv-years').value); var resultDiv = document.getElementById('inv-result');

// Validation if (isNaN(principal) || principal Please enter a valid initial investment (0 or more).'; return; } if (isNaN(annualRate) || annualRate 100) { resultDiv.innerHTML = 'Please enter a valid annual interest rate between 0 and 100.'; return; } if (isNaN(years) || years 100) { resultDiv.innerHTML = 'Please enter a valid investment period between 1 and 100 years.'; return; } if (principal === 0 && contribution === 0) { resultDiv.innerHTML = 'Please enter an initial investment or regular contribution greater than 0.'; return; }

var r = annualRate / 100; var n = compoundFreq; var t = years;

// Future value of lump sum: FV = P * (1 + r/n)^(n*t) var fvPrincipal = principal * Math.pow(1 + r / n, n * t);

// Future value of regular contributions (annuity): // FV_annuity = PMT * [((1 + r/n)^(n*t) - 1) / (r/n)] * (1 + r/n)^(n/contribFreq - 1) // This calculator uses the general formula adjusting for contribution frequency vs compounding frequency: // Effective rate per contribution period = (1 + r/n)^(n/contribFreq) - 1 var fvContributions = 0; if (contribution > 0 && r > 0) { var effectiveRatePerPeriod = Math.pow(1 + r / n, n / contribFreq) - 1; var totalPeriods = contribFreq * t; fvContributions = contribution * ((Math.pow(1 + effectiveRatePerPeriod, totalPeriods) - 1) / effectiveRatePerPeriod); } else if (contribution > 0 && r === 0) { fvContributions = contribution * contribFreq * t; }

var totalFV = fvPrincipal + fvContributions; var totalContributions = principal + contribution * contribFreq * t; var totalInterest = totalFV - totalContributions;

// Build year-by-year table var tableRows = ''; for (var yr = 1; yr 0 && r > 0) { var effRate = Math.pow(1 + r / n, n / contribFreq) - 1; var periods_yr = contribFreq * yr; fvC_yr = contribution * ((Math.pow(1 + effRate, periods_yr) - 1) / effRate); } else if (contribution > 0 && r === 0) { fvC_yr = contribution * contribFreq * yr; } var total_yr = fvP_yr + fvC_yr; var invested_yr = principal + contribution * contribFreq * yr; var interest_yr = total_yr - invested_yr; tableRows += '' + yr + '$' + invested_yr.toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2}) + '$' + interest_yr.toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2}) + '$' + total_yr.toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2}) + ''; } var tableNote = t > 50 ? 'Table shows first 50 years. Final values shown above.

' : '';

resultDiv.innerHTML = '### Results ' + '' + 'Initial Investment$' + principal.toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2}) + '' + 'Total Contributions$' + (contribution * contribFreq * t).toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2}) + '' + 'Total Amount Invested$' + totalContributions.toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2}) + '' + 'Total Interest Earned$' + totalInterest.toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2}) + '' + 'Future Value After ' + t + ' Years$' + totalFV.toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2}) + '' + '' + '#### Year-by-Year Breakdown ' + '' + '' + 'YearTotal InvestedInterest EarnedBalance' + '' + tableRows + '' + '' + tableNote; }

#### Formulas Used

Future Value of Lump Sum (Compound Interest):

FVprincipal = P × (1 + r/n)n×t

Future Value of Regular Contributions (Annuity):

Effective rate per period: i = (1 + r/n)n/f − 1

FVcontributions = PMT × [((1 + i)f×t − 1) / i]

Total Future Value:

FVtotal = FVprincipal + FVcontributions

Where: P = principal, r = annual interest rate (decimal), n = compounding frequency per year, t = time in years, f = contribution frequency per year, PMT = regular contribution amount.

#### Assumptions & References

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References

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