UK mortgage guide · Last reviewed 25 July 2026
How mortgage repayments work
On a repayment mortgage, each monthly payment usually covers interest charged for the period and repays some of the amount borrowed. At the beginning of a long mortgage, a larger share of each payment is normally interest because the outstanding balance is higher.
The three main inputs
The amount borrowed, interest rate and mortgage term are the core inputs. Holding two steady while increasing the third can materially alter the monthly payment or total interest. A calculator shows the maths; a lender decides what it will offer and whether it is affordable.
Monthly payment versus total interest
A longer term can reduce the required monthly payment, but interest may be charged for more years. A shorter term can increase the payment while reducing total interest. Compare both measures, along with how the term fits your circumstances.
Rates, deals and fees
Many mortgages have an initial fixed or discounted rate followed by a different lender rate. Product fees, early repayment charges and refinancing costs can change the overall comparison. A future rate cannot be known from a simple illustration.
Overpayments
Overpaying can reduce the balance and future interest, but mortgage terms may limit how much you can overpay without an early repayment charge. Check the product terms and keep an appropriate emergency buffer before committing money.
Official and independent information
This guide is educational information, not a mortgage recommendation or advice.