Understanding Mortgage Payments
Last reviewed: 8 October 2026
A repayment mortgage payment normally covers both interest and part of the amount borrowed. If the rate and schedule stay unchanged, the balance should reach zero by the end of the term.
What changes the monthly payment?
The main inputs are the amount borrowed, interest rate and term. Borrowing more raises the payment. A higher rate also raises the payment. Extending the term usually lowers the monthly payment but can increase the total interest paid.
Why early payments contain more interest
Interest is charged on the outstanding balance. Early in the mortgage the balance is at its highest, so a larger share of the payment usually goes toward interest. As the balance falls, more of the payment goes toward principal.
Deposit and LTV
Your deposit reduces the mortgage required. Loan-to-value compares the mortgage with the property value. Borrowing £180,000 on a £200,000 property is 90% LTV.
Fixed and variable rates
A fixed rate stays unchanged for an agreed period. A variable or tracker rate can move, so monthly payments can change. A calculator using one fixed rate cannot forecast future variable-rate payments.
What calculators leave out
Arrangement fees, valuation costs, legal costs, insurance, taxes, early-repayment charges and lender affordability tests can all matter. Use the lender's official illustration for an actual product.
Official consumer guidance
MoneyHelper explains repayment and interest-only mortgage structures in more detail: mortgage repayment options.