Mortgage Overpayment Calculator
See how much interest and time you save by overpaying your mortgage each month.
How it works
The calculator adds your extra amount to the normal payment and works out how many months it then takes to clear the balance at the same rate. The difference in months and in interest paid is your saving.
Example: on a 200,000 balance at 5% over 25 years, paying 200 extra a month clears the mortgage in about 18.8 years, saves about 6.2 years and roughly 41,800 in interest. Many fixed deals limit penalty-free overpayments, often to 10% of the balance a year, so check your terms.
Frequently asked questions
Is overpaying always a good idea?
It saves interest, but compare it with other uses of cash, such as an emergency fund or higher-interest debt.
Will I be charged for overpaying?
Some deals charge early repayment fees above a yearly limit. Ask your lender.
More calculators
Last updated October 2026. For information only, not financial advice.