Mortgage Overpayment Calculator
Work out exactly what overpaying your mortgage achieves: the interest saved, the years knocked off the term, and a side-by-side comparison of both futures.
Paid off the balance today
Year-by-year comparison
| Year | Balance (no overpaying) | Balance (overpaying) | Interest saved to date |
|---|---|---|---|
| 1 | £214,006 | £211,556 | £50 |
| 2 | £207,737 | £202,725 | £213 |
| 3 | £201,181 | £193,487 | £493 |
| 4 | £194,322 | £183,826 | £897 |
| 5 | £187,149 | £173,720 | £1,429 |
| 6 | £179,646 | £163,150 | £2,096 |
| 7 | £171,799 | £152,095 | £2,904 |
| 8 | £163,591 | £140,531 | £3,860 |
| 9 | £155,006 | £128,437 | £4,969 |
| 10 | £146,026 | £115,787 | £6,240 |
How does overpaying save so much?
Every pound you overpay reduces the balance that interest is charged on for every remaining month of the mortgage. Because your contractual payment stays the same, more of each subsequent payment goes to principal — the effect compounds, which is why modest overpayments produce outsized savings on long terms.
Worked example
On a £220,000 balance at 4.5% with 22 years remaining, overpaying £200 a month clears the mortgage about 4 years and 5 months early and saves £28,546 in interest.
Frequently asked questions
Is it worth overpaying my mortgage?
Overpaying saves interest at your mortgage rate, guaranteed and tax-free. Paying an extra £200 a month on a £220,000 balance at 4.5% with 22 years left saves about £28,546 in interest and clears the mortgage years early. Compare that against higher-interest debts and your emergency fund first.
Do overpayments reduce my term or my monthly payment?
Most lenders let you choose. This calculator models the more powerful option: keeping your payment the same so the term shrinks. Reducing the monthly payment instead frees up cash flow but saves much less interest.
Are there limits on how much I can overpay?
Many fixed-rate deals allow up to 10% of the outstanding balance per year without an early repayment charge (ERC); some allow more, and tracker/SVR mortgages are often unlimited. Check your terms — an ERC can wipe out the benefit of a large lump sum.
Should I overpay the mortgage or invest instead?
Overpaying earns a guaranteed, risk-free 'return' equal to your mortgage rate. Investing may earn more over long periods but with risk. Many people split the difference; the right answer depends on your rate, time horizon, and appetite for risk.