See what an overpayment could save
Compare your current repayment mortgage with a regular monthly overpayment. The illustration assumes your interest rate stays the same for the remaining term.
This is a repayment-mortgage illustration only. It assumes a constant rate, monthly payments and no lender fees or early repayment charges. Check your lender's overpayment allowance before acting.
Buying or remortgaging? Use our UK Mortgage Calculator to estimate a new mortgage's monthly repayment, total interest and loan-to-value.
How to use the UK Mortgage Overpayment Calculator
Compare a standard repayment mortgage with the same mortgage plus an extra monthly payment. The results show the estimated interest and time saved if the rate stays unchanged.
Enter your current mortgage details
Use the balance you still owe, your current annual rate and the years remaining. This is for a repayment mortgage, where each regular payment covers interest and capital.
Add an affordable monthly overpayment
Enter the extra amount you expect to pay each month. The calculator keeps the normal repayment constant and applies the extra amount to reduce the balance faster.
Compare interest and time saved
Review the no-overpayment and overpayment illustrations together. Check your lender’s annual overpayment allowance and any early repayment charge before paying extra.
Frequently Asked Questions
What does the UK Mortgage Overpayment Calculator calculate?
It compares a repayment mortgage with and without an extra monthly payment. It estimates the interest saved, time saved and new combined monthly payment from your current balance, interest rate and remaining term.
How does a monthly mortgage overpayment reduce interest?
The extra payment reduces the capital balance earlier. As interest is normally charged on the outstanding balance, future monthly interest is lower and more of each regular payment can reduce capital.
Does an overpayment reduce my monthly payment or the term?
This illustration keeps the normal repayment payment unchanged and shows the term reducing. Some lenders may instead reduce the required payment, or offer a choice, so check how your lender treats overpayments.
Can I make unlimited mortgage overpayments?
Not always. Fixed-rate deals often limit fee-free overpayments and may charge an early repayment charge if you exceed the allowance. Check your mortgage offer or ask your lender before making an overpayment.
Why could my lender's figures differ?
Your lender may calculate interest daily, use a different payment date, change your payment after an overpayment, charge fees, or apply a rate that changes over time. This is a planning illustration, not a settlement quote.
Does this work for interest-only mortgages?
No. The calculator is designed for repayment mortgages. With an interest-only mortgage, the normal payment usually does not reduce the capital, so the comparison needs different assumptions.
Is my information stored?
No. Calculations run locally in your browser.