Calculate how much interest you could save and how many months you could cut from your mortgage by making regular overpayments.
This calculator provides estimates only. It does not constitute financial advice. Most UK mortgages allow up to 10% overpayment per year without early repayment charges (ERCs), but check your specific mortgage terms. Always consult your lender or a qualified mortgage adviser.
Making regular overpayments on your mortgage is one of the most effective ways to reduce the total amount of interest you pay and shorten your mortgage term. Even small monthly overpayments can save thousands of pounds over the life of a typical UK mortgage, because each overpayment reduces the outstanding balance on which interest is calculated. This calculator shows you exactly how much interest you could save and how many months you could knock off your mortgage by making regular monthly overpayments. It also warns you if your planned overpayments exceed the typical annual limit that most UK lenders impose, helping you avoid early repayment charges (ERCs). The line chart compares your standard repayment balance against the overpayment balance over time, so you can see the impact visually.
To calculate your mortgage overpayment savings: 1. Enter your outstanding mortgage balance. This is the amount you currently owe, not the original loan amount. Check your latest mortgage statement for the exact figure. 2. Enter your current interest rate. This is the annual rate charged by your lender. If you are on a fixed rate, enter that. If you are on a variable or tracker rate, enter the current rate. 3. Set your remaining mortgage term in years. This is how many years are left until your mortgage would be fully repaid under normal payments. 4. Enter the monthly overpayment amount you are considering. Even GBP 100-200 per month can make a significant difference over time. 5. Check the advanced options to adjust the annual overpayment limit. Most UK lenders allow 10% of the outstanding balance per year without charges, but check your specific terms. 6. Review the results. The calculator shows you the interest saved, months saved, and warns you if your overpayments would exceed the annual limit, risking early repayment charges.
The calculator simulates two repayment schedules month by month: one with standard payments only, and one with your additional overpayments included. The standard monthly payment is calculated using the annuity formula: M = P x [r(1+r)^n] / [(1+r)^n - 1], where P is the outstanding balance, r is the monthly interest rate (annual rate divided by 12), and n is the total number of remaining monthly payments. For the overpayment schedule, the same standard payment is made each month, plus your additional overpayment. Each extra payment goes directly towards reducing the principal balance, which means less interest accrues in subsequent months. This creates a compounding effect where the benefits of overpaying grow over time. The interest saved is the difference between total interest paid under the standard schedule and total interest paid under the overpayment schedule. Months saved is the difference in how long it takes to clear the balance completely. The ERC check compares your cumulative annual overpayments against the specified percentage limit of your balance at the start of each year. If your overpayments exceed this limit in any year, a warning is displayed.
Most UK fixed-rate mortgages allow you to overpay up to 10% of the outstanding balance per year without early repayment charges. Some tracker and variable rate mortgages have no overpayment restrictions at all. Always check your specific mortgage terms before committing to regular overpayments. Early repayment charges (ERCs) typically apply during your fixed or discounted rate period and can range from 1% to 5% of the amount overpaid above the limit. Once you move to your lender's standard variable rate (SVR), ERCs usually no longer apply. Before overpaying your mortgage, consider whether you have an adequate emergency fund (typically 3-6 months of expenses), whether you have any higher-interest debts to clear first, and whether you are maximising any employer pension contributions. The FCA recommends that consumers consider their overall financial position before making overpayments.