Mortgage calculator with overpayments
Work out your monthly mortgage payment and total interest, then see how much sooner you’d be mortgage-free and what you’d save by overpaying.
- Monthly payment
- £1,461.48
- to repay £250,000 over 25 years at 5%
- Total interest
- £188,441
- without overpaying
- Total repaid
- £438,441
- loan and interest
- Mortgage-free by
- October 2051
- with the first payment in November 2026
Paying £5,000 straight away saves £12,023 in interest and clears the mortgage 11 months sooner, in November 2050 instead of October 2051.
- Interest saved
- £12,023
- Mortgage-free sooner by
- 11 months
- New end date
- November 2050
Show the figures for each year
| Year | Interest | Overpaid | Balance with overpayments | Balance without |
|---|---|---|---|---|
| 1 | £12,127 | £5,000 | £239,589 | £244,845 |
| 2 | £11,850 | £0 | £233,902 | £239,427 |
| 3 | £11,559 | £0 | £227,923 | £233,731 |
| 4 | £11,253 | £0 | £221,639 | £227,744 |
| 5 | £10,932 | £0 | £215,033 | £221,450 |
| 6 | £10,594 | £0 | £208,090 | £214,835 |
| 7 | £10,239 | £0 | £200,790 | £207,881 |
| 8 | £9,865 | £0 | £193,118 | £200,571 |
| 9 | £9,473 | £0 | £185,053 | £192,887 |
| 10 | £9,060 | £0 | £176,575 | £184,811 |
| 11 | £8,626 | £0 | £167,664 | £176,320 |
| 12 | £8,170 | £0 | £158,297 | £167,396 |
| 13 | £7,691 | £0 | £148,450 | £158,015 |
| 14 | £7,187 | £0 | £138,100 | £148,154 |
| 15 | £6,658 | £0 | £127,220 | £137,789 |
| 16 | £6,101 | £0 | £115,783 | £126,893 |
| 17 | £5,516 | £0 | £103,762 | £115,440 |
| 18 | £4,901 | £0 | £91,125 | £103,400 |
| 19 | £4,255 | £0 | £77,842 | £90,745 |
| 20 | £3,575 | £0 | £63,879 | £77,443 |
| 21 | £2,861 | £0 | £49,202 | £63,460 |
| 22 | £2,110 | £0 | £33,774 | £48,761 |
| 23 | £1,320 | £0 | £17,557 | £33,310 |
| 24 | £491 | £0 | £510 | £17,069 |
| 25 | £2 | £0 | £0 | £0 |
This uses standard UK monthly interest: the yearly rate divided by 12, so 5% a year is 0.417% a month, with the payment worked out to clear the loan over the term and rounded to the penny. Overpayments keep your monthly payment the same and shorten the term; some lenders lower the payment instead. A lump sum goes in at the start of the year you choose. Many lenders let you overpay up to 10% a year without a charge, and you could be charged an early repayment charge for going over your deal’s limit, so check your own deal. The warning here measures the 10% against what you’d owe at the start of each year. The rate stays the same for the whole term here, although in practice it changes when a fixed or tracker deal ends. Fees, insurance and lender rounding aren’t included. Rules as of September 2026.
Use this calculator for a UK repayment or interest-only mortgage, including one-off lump sums. To compare a rate change when a fixed deal ends, or a US loan, use the mortgage cost calculator.
What goes in
Put in the amount you’re borrowing, or the price and your deposit, then the interest rate and the term. Choose repayment, where each payment clears some of the loan, or interest only, where you pay just the interest and still owe the whole loan at the end. If you plan to pay extra, add a monthly overpayment, a one-off lump sum and the year you’d pay it.
What the result means
The example is a £250,000 repayment mortgage at 5% over 25 years. That’s £1,461.48 a month and £188,441 in interest. Paying £5,000 off straight away, and keeping the monthly payment the same, clears it 11 months sooner and saves £12,023 in interest.
For the same example, MoneyHelper says you’d repay 11 months earlier and save £11,970 in interest. Differences like that can come from when a lender applies the lump sum and how it works out interest, so your lender’s figures may differ a little.
How it’s worked out
It uses standard UK monthly interest: the yearly rate divided by 12. The payment is the fixed amount that clears the loan over the term, rounded to the penny. Overpayments here keep the payment the same and shorten the term; some lenders lower your payment instead unless you ask them to shorten the term. The rate stays the same throughout, although yours will change when a fixed deal ends.
MoneyHelper says many lenders let you overpay up to 10% a year without penalties, and that you could be charged for going over your agreed limit. That charge is usually an early repayment charge. The calculator warns you when your overpayments in a year come to more than 10% of what you’d owe at the start of that year, but lenders set their limits in different ways, so check your own deal before you pay.
Sources
- Should you pay off your mortgage early?, MoneyHelper