A lower monthly payment can come with a higher overall cost. Spreading repayment over more years usually reduces the monthly amount while leaving the balance outstanding for longer. Compare both figures, not just the payment that looks easiest today.
A worked illustration
The table uses a £200,000 repayment mortgage at an illustrative annual rate of 4.5%, held unchanged for the entire term. It assumes equal monthly payments, no fees and no overpayments. These are mathematical illustrations, not available product rates or lender quotes.
| Term | Monthly repayment | Total repaid | Interest within total |
|---|---|---|---|
| 20 years | £1,265 | £303,672 | £103,672 |
| 25 years | £1,112 | £333,499 | £133,499 |
| 30 years | £1,013 | £364,813 | £164,813 |
Monthly figures are rounded for display; totals use the unrounded calculation. Actual lender calculations and payments may differ. Changing the interest rate would change every figure in the table.
What does the comparison tell you?
In this illustration, the longer term creates more room in the monthly budget, but interest runs for more years. It does not show which term is suitable for any particular person. Your income, commitments, age, plans and the lender’s criteria need to be considered.
Try one change at a time
- Open the mortgage repayment calculator and enter an illustrative amount, rate and term.
- Keep the amount and rate the same while changing only the term.
- Compare monthly repayments, total repaid and total interest.
- Reset the term, then explore a different illustrative rate.
- Write down the trade-offs you want to discuss with an adviser.
What the calculator does not decide
It does not assess affordability, eligibility or a lender’s offer. It also does not model every fee, future rate change, early repayment charge or overpayment rule. Do not assume you can make unrestricted overpayments later to undo the cost of a longer term.
Your home may be repossessed if you do not keep up repayments on your mortgage.
Sources and further reading
Sources checked on 28 October 2026. General information only, not a personal mortgage recommendation. Your circumstances, the property and lender criteria affect the options available.