What a mortgage really costs — the monthly payment, the total interest, and what a small overpayment could save you.
| Loan amount | Per month | Total interest | Total repaid |
|---|---|---|---|
| £150,000 | £833.75 | £100,124.62 | £250,124.62 |
| £200,000 | £1,111.66 | £133,499.49 | £333,499.49 |
| £250,000 | £1,389.58 | £166,874.36 | £416,874.36 |
| £300,000 | £1,667.50 | £200,249.23 | £500,249.23 |
| £350,000 | £1,945.41 | £233,624.10 | £583,624.10 |
| £400,000 | £2,223.33 | £266,998.97 | £666,998.97 |
Each monthly payment covers that month's interest plus a slice of the loan itself. Early on, most of your payment is interest because the balance is at its biggest; as the balance falls, more of each payment chips away at the loan. That's why the total interest on a 25-year mortgage can rival the amount you borrowed — £166,874 on a £250,000 loan at 4.5%.
Overpaying attacks the balance directly, so every future month's interest shrinks too. Even £100–£200 a month can take years off the term. Two checks before you start: most fixed deals allow penalty-free overpayments of up to 10% of the balance a year (going over can trigger early repayment charges), and keep an emergency fund first — money paid into a mortgage is hard to get back out.
LTV (loan-to-value) is your loan divided by the property price. Dropping into a lower LTV band — 90%, 80%, 75%, 60% — usually unlocks cheaper rates at remortgage time, which is another reason overpayments and a bigger deposit pay off twice.
Buying costs more than the deposit and the loan: stamp duty is due on top. Work it out with our stamp duty calculator, and check the payment against your real budget with the take-home pay calculator.
At 4.5% over 25 years: £1,389.58 a month, £166,874 total interest across the term.
On £250,000 at 4.5% over 25 years, £200 a month extra clears the loan about 5 years early and saves roughly £38,458 of interest. Check your lender's overpayment allowance first — many fixes cap penalty-free overpayments at 10% of the balance per year.
Loan-to-value: your loan as a percentage of the price. Lower bands (90/80/75/60%) usually mean cheaper rates.
No — that's a lender's affordability assessment. This shows what a given loan costs.