Calculate Average Interest Rate on Multiple Loans

Amortization Schedule Calculator

This calculator helps you understand how your loan principal and interest payments are distributed over the life of the loan. Amortization is the process of paying off a debt over time in equal installments. Each payment you make consists of two parts: principal and interest. Initially, a larger portion of your payment goes towards interest, and a smaller portion goes towards the principal. As you continue to make payments, this ratio gradually shifts, with more going towards the principal and less towards interest. This calculator will generate an amortization schedule showing the breakdown for each payment period.

function calculateAmortization() { var loanAmount = parseFloat(document.getElementById("loanAmount").value); var annualInterestRate = parseFloat(document.getElementById("annualInterestRate").value); var loanTermYears = parseFloat(document.getElementById("loanTermYears").value); var paymentFrequency = parseInt(document.getElementById("paymentFrequency").value); var resultsDiv = document.getElementById("amortizationSchedule"); resultsDiv.innerHTML = "

Amortization Schedule

"; // Clear previous results if (isNaN(loanAmount) || isNaN(annualInterestRate) || isNaN(loanTermYears) || loanAmount <= 0 || annualInterestRate < 0 || loanTermYears <= 0) { resultsDiv.innerHTML += "Please enter valid positive numbers for all fields."; return; } var monthlyInterestRate = (annualInterestRate / 100) / paymentFrequency; var numberOfPayments = loanTermYears * paymentFrequency; // Calculate monthly payment using the loan payment formula var monthlyPayment; if (monthlyInterestRate === 0) { monthlyPayment = loanAmount / numberOfPayments; } else { monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1); } var remainingBalance = loanAmount; var totalInterestPaid = 0; var totalPrincipalPaid = 0; var tableHtml = ""; tableHtml += ""; tableHtml += ""; tableHtml += ""; tableHtml += ""; for (var i = 1; i <= numberOfPayments; i++) { var interestPayment = remainingBalance * monthlyInterestRate; var principalPayment = monthlyPayment – interestPayment; // Adjust last payment to account for rounding if (i === numberOfPayments) { principalPayment = remainingBalance; monthlyPayment = interestPayment + principalPayment; } remainingBalance -= principalPayment; totalInterestPaid += interestPayment; totalPrincipalPaid += principalPayment; // Ensure remaining balance doesn't go negative due to floating point inaccuracies if (remainingBalance < 0.01) { remainingBalance = 0; } tableHtml += ""; tableHtml += ""; tableHtml += ""; // Placeholder for payment date, can be complex to calculate accurately without start date tableHtml += ""; tableHtml += ""; tableHtml += ""; tableHtml += ""; tableHtml += ""; } tableHtml += ""; tableHtml += "

Payment #	Payment Date	Payment Amount	Principal Paid	Interest Paid	Remaining Balance
" + i + "	TBD	$" + monthlyPayment.toFixed(2) + "	$" + principalPayment.toFixed(2) + "	$" + interestPayment.toFixed(2) + "	$" + remainingBalance.toFixed(2) + "

"; resultsDiv.innerHTML += "Your estimated monthly payment: $" + monthlyPayment.toFixed(2) + ""; resultsDiv.innerHTML += "Total Principal Paid: $" + totalPrincipalPaid.toFixed(2) + ""; resultsDiv.innerHTML += "Total Interest Paid: $" + totalInterestPaid.toFixed(2) + ""; resultsDiv.innerHTML += tableHtml; }