A £250,000 repayment mortgage at 4.5% over 25 years costs £1,389.58 a month — you repay £416,874 in total, including £166,874 of interest. Change the loan, rate and term below to see your own figures instantly.
Capital-and-interest repayment mortgage
Lenders work out your monthly payment with the standard amortisation formula — the same maths every UK bank and building society uses for a capital-and-interest (repayment) mortgage. Each monthly payment covers that month’s interest first, then chips away at the capital you still owe, so the balance falls a little faster every year.
The formula:
M = P · r · (1 + r)n ÷ ( (1 + r)n − 1 )
P = loan amount · r = monthly rate (annual rate ÷ 12 ÷ 100) · n = number of payments (years × 12). Total repaid = M × n; total interest = total repaid − P.
With P = £250,000, an annual rate of 4.5% and a 25-year term, r = 0.045 ÷ 12 = 0.00375 and n = 300 payments. The formula gives a monthly payment of £1,389.58. Over the full 25 years you repay 300 × £1,389.58 = £416,874, of which £166,874 is interest.
Two levers drive your monthly payment: the interest rate and the term. A higher rate lifts every payment; a longer term lowers the monthly payment but adds years of interest. The table shows the monthly cost of a £250,000 mortgage at a range of rates and terms.
| Rate | 25-year monthly | 30-year monthly |
|---|---|---|
| 3.5% | £1,251.56 | £1,122.61 |
| 4.5% | £1,389.58 | £1,266.71 |
| 5.5% | £1,535.22 | £1,419.47 |
| 6.5% | £1,688.02 | £1,580.17 |
On an interest-only mortgage you pay just the interest each month — loan × rate ÷ 12 — and the capital stays untouched, so you still owe the full amount at the end of the term and need a separate plan to repay it. The monthly cost is lower, but you never reduce the debt. Use the Interest-only toggle above to compare.
On a £250,000 repayment mortgage at 4.5% over 25 years the monthly payment is £1,389.58. Over the full term you repay £416,874, including £166,874 of interest. A higher rate or longer term raises the cost; a bigger deposit lowers it.
Lenders use the standard amortisation formula: M = P·r·(1+r)n ÷ ((1+r)n − 1), where P is the loan, r is the monthly rate (annual rate ÷ 12 ÷ 100) and n is the number of monthly payments (years × 12). Each payment covers the month’s interest plus a slice of capital.
Total interest is the total repaid minus the amount borrowed. On £250,000 at 4.5% over 25 years you repay £416,874 in total, so £166,874 is interest. Overpaying, or choosing a shorter term, cuts the interest considerably.
No — it’s an estimate using the standard amortisation maths. Your lender’s figures may differ slightly for product fees, fixed-then-variable rates, or daily-interest calculations. Always check the official illustration from your lender before you commit.
