Mortgage Overpayment Calculator
Find out how much interest and time you could save by overpaying your mortgage.
| No overpayment | With overpayment | |
|---|---|---|
| Monthly payment | £1,169.18 | £1,369.18 |
| Time to clear | 25 years | 18 years 10 months |
| Total interest | £150,754 | £108,911 |
| Interest saved | £41,843 |
Assumes a fixed rate for the whole term and that the overpayment reduces your balance straight away. Many fixed deals limit penalty-free overpayments (often around 10% of the balance a year), so check yours before paying extra.
Why overpaying a mortgage saves so much
Mortgage interest is charged on the balance you still owe. Every pound you overpay reduces that balance straight away, so you stop paying interest on it for the rest of the term. Because the saving compounds, overpaying early in the mortgage has the biggest effect.
Example: overpaying £200 a month on a £200,000 mortgage at 5% over 25 years saves about £41,843 in interest and clears the mortgage roughly 6 years 2 months sooner.
Check before you overpay
- Overpayment limits: many fixed deals let you overpay up to about 10% of the balance each year without charge. Above that you may pay an early repayment charge.
- Tell your lender to apply the overpayment to the balance, not to future payments.
- Compare with other uses of your money: clearing high-interest debt or building an emergency fund usually comes first, and savings interest may be lower than your mortgage rate.
Reducing the term or the payment
Most lenders let you either keep your payment the same and finish sooner (saving the most interest), or lower your monthly payment. This calculator shows the first option.
Frequently asked questions
Is it worth overpaying my mortgage?
Often yes if your mortgage rate is higher than the interest you would earn on savings, and you have an emergency fund. It saves interest and shortens the mortgage.
How much can I overpay without a penalty?
Many fixed-rate deals allow around 10% of the outstanding balance each year. Your mortgage paperwork or lender will confirm your limit.
Should I overpay or save instead?
If your mortgage rate is higher than the after-tax savings rate, overpaying usually wins. Savings keep the money accessible, while overpayments are hard to take back.
What happens at the end of my fixed rate?
You move to a new deal or the lender’s standard variable rate. This calculator assumes one rate throughout, so results will change if your rate does.
More from UK Answers
Figures are for the 2026/27 tax year from official sources and are estimates for guidance only, not financial or legal advice. Printed from ukanswers.co.uk.