Free mortgage overpayment calculator
Cut the term. Keep the house.
Work out how overpaying your mortgage — with extra monthly payments or a lump sum — saves interest over the life of the loan and how many months you knock off the final settlement.
Knocked off the term
5 years 1 month
Mortgage settled in 19 years 11 months instead of 25 years.
Interest saved
£38,458
Debt-free date
September 2046
Standard monthly payment
£1,389.58
With overpayment
£1,589.58
Original interest
£166,874
Interest after overpaying
£128,416
Remaining balance
How the outstanding balance falls with and without overpayments.
Year-by-year balanceShowHide
| Year | No overpay | With overpay |
|---|---|---|
| Start | £250,000 | £250,000 |
| 1 | £244,462 | £242,012 |
| 2 | £238,669 | £233,656 |
| 3 | £232,610 | £224,917 |
| 4 | £226,273 | £215,776 |
| 5 | £219,645 | £206,216 |
| 6 | £212,712 | £196,216 |
| 7 | £205,461 | £185,757 |
| 8 | £197,876 | £174,817 |
| 9 | £189,943 | £163,375 |
| 10 | £181,646 | £151,407 |
| 11 | £172,968 | £138,889 |
| 12 | £163,891 | £125,796 |
| 13 | £154,397 | £112,102 |
| 14 | £144,466 | £97,778 |
| 15 | £134,080 | £82,797 |
| 16 | £123,216 | £67,127 |
| 17 | £111,853 | £50,738 |
| 18 | £99,969 | £33,595 |
| 19 | £87,538 | £15,665 |
| 20 | £74,536 | £0 |
| 21 | £60,937 | £0 |
| 22 | £46,713 | £0 |
| 23 | £31,836 | £0 |
| 24 | £16,276 | £0 |
| 25 | £0 | £0 |
Overpayments reduce the balance first, so later months charge interest on a smaller loan.
Keeping the contractual payment the same is what knocks months off the end date — the extra is not treated as a holiday.
A lump sum today has more effect than the same money spread later, because every remaining month of interest is smaller.
Mortgage overpayment questions
Each question opens a full guide. The short version is here; the longer answer is on its own page.
What is a mortgage overpayment calculator?
It shows how extra monthly payments or a lump sum overpayment cut the outstanding mortgage balance, how much interest you save over the remaining term, and how many months you knock off the final settlement.
Read the full answerHow much can I save by overpaying my mortgage?
It depends on the balance, rate, remaining term and how much you overpay. Because interest is charged on what you still owe, even a modest extra payment can save thousands and shorten the term by years.
Read the full answerDo overpayments reduce the term or the monthly payment?
This calculator keeps the standard repayment the same, so the extra goes to capital and the mortgage is settled sooner. Some lenders will instead reduce the monthly payment and keep the original end date — that usually saves less interest.
Read the full answerIs there a limit on extra mortgage payments?
Many fixed-rate deals allow penalty-free overpayments of around 10% of the balance each year. A larger lump sum can trigger an early repayment charge. Check your offer document before you overpay.
Read the full answerDoes overpaying always save interest?
On a repayment mortgage, yes — a lower balance means less interest in later months. Offset, interest-only, or products with fees can work differently, so treat the result as an illustration rather than a quote.
Read the full answer