How to use
Enter how much you are borrowing (the property price minus your deposit), the mortgage term and the interest rate. You get the monthly repayment, the total interest and the total amount repayable. Open “Repayment schedule by year” to see how much of each year’s payments goes to capital and to interest, and what you still owe at the end of each year.
The starting figures (£200,000 over 25 years at 4.5%) are only an example. Replace them with your own.
- Fixed-rate deal ending: most UK mortgages start on a 2- or 5-year fixed or tracker rate. Add a rate change, for example “from year 6 the rate is 7%”, to see the payment on the lender’s SVR. You can add up to four changes, which also works for modelling remortgaging at a lower rate.
- Interest-only years: during these years you pay only interest. The capital is then repaid over the rest of the term, so the payment jumps when the period ends.
- Repayment type: almost every UK repayment mortgage uses capital and interest with a level monthly payment. Fixed capital (the payment starts high and falls every month) is shown for comparison.
How the repayment is calculated
With a capital-and-interest mortgage, each payment covers that month’s interest first, and the rest pays off the capital. Early payments are mostly interest; later ones are mostly capital.
Monthly repayment = P × r × (1 + r)^n ÷ [(1 + r)^n − 1]
P is the amount borrowed, r is the monthly rate (annual rate ÷ 12) and n is the number of payments (years × 12).
When the rate changes, the payment is recalculated from the balance left and the number of payments remaining, which is what happens when a fixed deal ends.
Example
£200,000 over 25 years at 4.5%:
| Repayment type | Monthly repayment | Total interest |
|---|---|---|
| Capital and interest | about £1,112 | about £133,500 |
| Fixed capital | £1,417 in the first month, falling to £669 | about £112,900 |
| Interest-only | £750 (the £200,000 is still owed at the end) | £225,000 over 25 years |
A rate 0.25 points higher (4.75%) adds about £29 a month. After a 5-year fix you would still owe about £175,700, and at a 7% SVR the payment would rise to about £1,362.
The Bank of England’s Bank Rate was 3.75% in October 2026, with the next decision due on 5 November 2026. Tracker mortgages move with it straight away; fixed rates only change when you take a new deal.
What this calculator leaves out
- Fees: arrangement, valuation and broker fees. If you add a fee to the loan, include it in the amount borrowed.
- Stamp Duty and buying costs: these are paid up front, not through the mortgage.
- Overpayments: paying extra shortens the term and cuts interest, but this page assumes you pay only the scheduled amount. Most fixed deals let you overpay up to 10% a year without an early repayment charge.