Turn a loan amount, interest rate and term into a clear monthly repayment — plus the total interest and total cost over the life of the mortgage. Adjust any figure to see the impact instantly.
Capital & interest repayment basis
A repayment (capital-and-interest) mortgage spreads the loan over the term so that the balance reaches zero by the end. Each monthly payment covers the interest due that month plus a slice of the capital. Early on, most of the payment is interest; later, more goes towards clearing the balance.
The standard amortisation formula is:
where P is the loan, r is the monthly interest rate (annual rate ÷ 12) and n is the number of monthly payments (years × 12). The calculator above runs this for you and totals the interest.
Two levers move your monthly payment the most — the interest rate and the term. Here’s a £220,000 mortgage at different rates over 25 years:
| Rate | Monthly | Total interest |
|---|---|---|
| 3.5% | £1,102 | £110,400 |
| 4.5% | £1,223 | £146,900 |
| 5.5% | £1,351 | £185,400 |
| 6.5% | £1,486 | £225,700 |
Most UK lenders cap borrowing at around 4 to 4.5 times your annual income, subject to affordability checks on your spending and existing debts. On a £40,000 salary that’s roughly £160,000–£180,000. Your deposit size, credit history and the lender’s stress-test rate all affect the final figure. Check your net pay with the take-home calculator before committing to a monthly payment.
On a £200,000 repayment mortgage at 4.5% over 25 years, the monthly payment is about £1,112, with roughly £133,500 of interest over the full term.
It uses the amortisation formula M = P × r(1+r)ⁿ / ((1+r)ⁿ − 1), where P is the loan, r the monthly rate and n the number of payments. Each instalment pays the month’s interest plus a slice of capital.
Typically around 4–4.5× your annual income, subject to affordability. On £40,000 that’s roughly £160,000–£180,000, but your deposit, outgoings and credit profile all play a part.
No — this assumes a repayment (capital-and-interest) mortgage, the most common type. On interest-only the monthly cost is just the interest, and the full capital is still owed at the end.
