How Do Mortgage Repayments Work?
Updated August 2026
A simple guide to mortgage repayments, including capital, interest, repayment terms, rates and why monthly payments can change.
What is a mortgage repayment?
A mortgage is a long-term loan used to buy property. On a repayment mortgage, your monthly payment normally covers interest plus part of the amount you borrowed, known as the capital or principal.
If you keep making the required payments, the outstanding balance should gradually reduce until the mortgage is repaid at the end of the term.
Want to try the idea yourself? Use the Mortgage Repayment Calculator.
Why interest is a big part of the calculation
Mortgage interest is charged on a large balance over many years, so even a relatively small change in the rate can materially affect the monthly payment and total cost.
As the balance falls, the amount of interest charged can fall too, assuming the rate stays the same.
If you want to explore this topic further, see How to Calculate Loan Repayments.
What does the mortgage term change?
A longer term generally lowers the required monthly payment because the balance is spread over more payments. The downside is that interest may be charged for longer, increasing the total amount paid.
A shorter term normally means higher monthly payments but can reduce the total interest if the rate and other terms are unchanged.
Useful Wid9et tools related to this guide
Fixed, variable and changing payments
With a fixed-rate deal, the interest rate is fixed for an agreed period, which normally keeps the required payment predictable during that deal. Variable or tracker rates can move, causing repayments to rise or fall.
When a fixed deal ends, the new rate can change the payment significantly, so it is useful to model different rates rather than assuming today’s payment will last for the full mortgage term.
Estimate a mortgage payment
Use the Mortgage Repayment Calculator to compare the effect of different loan amounts, interest rates and terms. It can help answer practical questions such as how much an extra 1% interest might add to the monthly payment.
The result is an estimate rather than a mortgage offer. Actual costs can also include product fees, valuation costs, insurance and other charges.
Try it yourself
Ready to put this into practice? Open the relevant Wid9et tools directly in your browser.