A mortgage is a significant financial commitment, and knowing your outstanding balance is crucial for financial planning, refinancing decisions, or simply understanding your net worth. The remaining mortgage balance calculator helps you estimate how much you still owe on your home loan after a certain number of payments.
How the Calculation Works
The calculation for the remaining mortgage balance involves a few steps, relying on the principles of amortizing loans. An amortizing loan means that each payment you make covers both interest and a portion of the principal, and over time, the proportion of principal paid increases.
Step 1: Calculate the Monthly Payment
First, we need to determine the fixed monthly payment amount. The formula for calculating the monthly payment (M) of an amortizing loan is:
Alternatively, a common formula derived from the same principles is:
B = M * [ 1 - (1 + i)^-(N-k) ] / i
Where:
M = Monthly payment
i = Monthly interest rate
N = Total number of payments (original loan term in months)
k = Number of payments made
This calculator uses the second formula for simplicity in implementation.
Key Inputs Explained:
Original Loan Amount: The total sum you borrowed to purchase your home.
Annual Interest Rate: The yearly percentage charged by the lender on the outstanding loan balance.
Original Loan Term (Years): The total duration of the loan, typically 15, 20, or 30 years.
Number of Payments Made: The count of monthly payments you have successfully completed so far.
Why Use This Calculator?
Financial Planning: Understand your current debt level.
Refinancing Decisions: Assess if refinancing to a lower rate or different term is beneficial based on your remaining balance and equity.
Home Equity Loans/Lines of Credit: Determine your available equity, which is often calculated as the home's current market value minus the remaining mortgage balance.
Budgeting: Plan for future mortgage payments and eventual payoff.
This calculator provides an estimate. Your lender's official statement is the definitive source for your exact mortgage balance.
function calculateRemainingMortgage() {
var originalLoanAmount = parseFloat(document.getElementById("originalLoanAmount").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTermYears").value);
var paymentsMade = parseFloat(document.getElementById("paymentsMade").value);
var resultDiv = document.getElementById("result-value");
resultDiv.textContent = "$0.00"; // Reset result
if (isNaN(originalLoanAmount) || isNaN(interestRate) || isNaN(loanTermYears) || isNaN(paymentsMade) ||
originalLoanAmount <= 0 || interestRate < 0 || loanTermYears <= 0 || paymentsMade = totalPayments) {
resultDiv.textContent = "$0.00";
alert("You have made all payments or more. The remaining balance is $0.00.");
return;
}
// Calculate Monthly Payment (M)
var monthlyPayment = 0;
if (monthlyInterestRate > 0) {
monthlyPayment = originalLoanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, totalPayments)) / (Math.pow(1 + monthlyInterestRate, totalPayments) – 1);
} else {
monthlyPayment = originalLoanAmount / totalPayments; // Simple division if interest rate is 0
}
// Calculate Remaining Balance (B) using: B = M * [ 1 – (1 + i)^-(N-k) ] / i
var remainingBalance = 0;
if (monthlyInterestRate > 0) {
remainingBalance = monthlyPayment * (1 – Math.pow(1 + monthlyInterestRate, -(totalPayments – paymentsMade))) / monthlyInterestRate;
} else {
remainingBalance = originalLoanAmount – (monthlyPayment * paymentsMade); // Simple remaining if interest rate is 0
}
// Ensure remaining balance is not negative due to rounding or edge cases
if (remainingBalance < 0) {
remainingBalance = 0;
}
resultDiv.textContent = formatCurrency(remainingBalance);
}
function formatCurrency(amount) {
return amount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}