Calculate your potential new monthly mortgage payments when remortgaging.
Estimated New Monthly Payment
£0.00
Based on your inputs, your estimated monthly payment is:
Understanding Remortgaging and Your New Payments
Remortgaging is the process of changing your current mortgage to a new one, either with your existing lender or a new one. This is often done to secure a better interest rate, switch to a different type of mortgage product, or to raise additional funds.
When you remortgage, your new lender or product will have its own set of terms, including an interest rate and a repayment term. The calculation below estimates your new monthly payment based on the principal amount you still owe, the new interest rate you've secured, and the remaining term of your mortgage. This helps you understand the immediate financial impact of your remortgage deal.
How the Calculation Works:
The calculation uses the standard mortgage payment formula, often referred to as an annuity formula, to determine the fixed monthly payment required to pay off a loan over a set period with compound interest.
The formula is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
M = Your total monthly mortgage payment.
P = The principal loan amount (your current mortgage balance).
i = Your monthly interest rate. This is calculated by dividing your annual interest rate by 12 (e.g., 4.5% annual rate becomes 0.045 / 12 = 0.00375 monthly).
n = The total number of payments over the loan's lifetime. This is calculated by multiplying the remaining term in years by 12 (e.g., 25 years remaining becomes 25 * 12 = 300 payments).
Key Inputs for Remortgaging:
Current Mortgage Balance (£): This is the amount you currently owe on your mortgage. For remortgaging, this is typically the amount you wish to borrow under the new deal.
New Annual Interest Rate (%): This is the interest rate offered by your new mortgage product. It's crucial to compare this against your current rate.
Remaining Term (Years): This is the number of years left until your mortgage is fully paid off. You can sometimes choose to extend or shorten this term when remortgaging, which will affect your monthly payments and the total interest paid.
Why Use This Calculator?
This calculator is a useful tool for:
Comparing different remortgage offers to see which one results in the lowest monthly payment.
Understanding the impact of a change in interest rate on your outgoings.
Assessing how adjusting your remaining term might affect your monthly budget.
Budgeting for your housing costs after securing a new mortgage deal.
Remember, this calculator provides an estimate. Actual mortgage offers may include additional fees and charges, and your final repayment amount might vary slightly. It's always advisable to consult with a qualified mortgage advisor for personalised advice.
function calculateRemortgage() {
var currentMortgageBalance = parseFloat(document.getElementById("currentMortgageBalance").value);
var newInterestRate = parseFloat(document.getElementById("newInterestRate").value);
var remainingTermMonths = parseInt(document.getElementById("remainingTermMonths").value);
var monthlyPaymentResult = document.getElementById("monthlyPayment");
// Clear previous results and errors
monthlyPaymentResult.textContent = "£0.00";
// Input validation
if (isNaN(currentMortgageBalance) || currentMortgageBalance <= 0) {
alert("Please enter a valid current mortgage balance.");
return;
}
if (isNaN(newInterestRate) || newInterestRate < 0) {
alert("Please enter a valid annual interest rate.");
return;
}
if (isNaN(remainingTermMonths) || remainingTermMonths <= 0) {
alert("Please enter a valid remaining term in years.");
return;
}
// Calculations
var monthlyInterestRate = newInterestRate / 100 / 12;
var numberOfPayments = remainingTermMonths * 12;
var monthlyPayment;
if (monthlyInterestRate === 0) {
monthlyPayment = currentMortgageBalance / numberOfPayments;
} else {
monthlyPayment = currentMortgageBalance * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
}
// Display result
if (isNaN(monthlyPayment) || !isFinite(monthlyPayment)) {
monthlyPaymentResult.textContent = "Error";
} else {
monthlyPaymentResult.textContent = "£" + monthlyPayment.toFixed(2);
}
}