How the monthly payment is calculated
Interest only: payment = loan × annual rate ÷ 12
r = annual rate ÷ 12, n = number of months
On a repayment mortgage each payment covers that month's interest and pays off some of the loan, so the balance reaches zero at the end of the term. On an interest-only mortgage you pay only the interest and still owe the full loan at the end.
Monthly payments on a 25-year repayment mortgage
| Loan | 3.5% | 4.5% | 5.5% |
|---|---|---|---|
| £150,000 | £750.94 | £833.75 | £921.13 |
| £200,000 | £1,001.25 | £1,111.66 | £1,228.17 |
| £250,000 | £1,251.56 | £1,389.58 | £1,535.22 |
| £300,000 | £1,501.87 | £1,667.50 | £1,842.26 |
Worked example
Borrowing £200,000 at 4.5% over 25 years costs £1,111.66 a month on a repayment mortgage. Over the full term you repay about £333,500, of which £133,499 is interest. On interest only, the payment would be £750 a month, but the £200,000 would still be owed after 25 years.
Overpayments
Most fixed-rate deals let you overpay up to 10% of the balance a year without early repayment charges. Even £100 a month extra can cut years off the term and save thousands in interest: enter it above to see the effect.
Buying a home? Work out the stamp duty too.
Frequently asked questions
What is the monthly payment on a £200,000 mortgage?
At 4.5% over 25 years, about £1,111.66 a month on a repayment mortgage, or £750 a month interest only.
How much interest will I pay on my mortgage?
On £200,000 at 4.5% over 25 years, about £133,499 in total, if the rate stays the same.
Is it worth overpaying my mortgage?
Usually yes if your mortgage rate is higher than what your savings earn after tax and you keep an emergency fund. Check your lender's overpayment limit to avoid early repayment charges.
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Last updated October 2026.