Mortgage Overpayment Calculator
Updated for the 2026/27 tax year (6 April 2026 – 5 April 2027)
Find out how much interest you could save, and how much sooner you could be mortgage-free, by overpaying every month or paying off a lump sum. Free, no sign-up. Nothing leaves your browser.
Balance year by year
| Year | Balance (normal) | Balance (overpaying) | Interest saved so far |
|---|
Why overpaying saves so much
Mortgage interest is charged on the balance you still owe. Every extra pound you pay reduces the balance straight away, so you are charged less interest every month after that for the rest of the mortgage. Overpayments made early in the term save the most, because they cut interest for the longest time.
Frequently asked questions
Is it worth overpaying my mortgage?
Overpaying saves interest at your mortgage rate, risk-free. It usually makes sense once you have an emergency fund and no more expensive debt. If your savings earn more after tax than your mortgage rate, saving may be better.
How much can I overpay without a penalty?
Most UK fixed and tracker deals let you overpay up to 10% of the outstanding balance each year without an early repayment charge. Check your mortgage offer, as limits vary.
Should I reduce my term or my monthly payment?
Keeping the payment the same and shortening the term saves the most interest. Some lenders recalculate your payment instead. Ask your lender which applies.