UK MORTGAGES · PLANNING GUIDE

What changes your monthly mortgage payment?

Your payment depends on more than the house price. The amount borrowed, interest rate, repayment term and mortgage type all matter—and fees can change the real cost.

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6 minute read · Reviewed 4 September 2026

Repayment versus interest-only

A capital repayment mortgage pays interest and reduces the balance each month. An interest-only mortgage generally covers interest during the term, leaving the borrowed capital to be repaid separately. The Get The Total calculator models a capital repayment mortgage.

Fixed and variable rates

A fixed rate normally stays unchanged for an agreed deal period, not necessarily the whole mortgage term. A variable or tracker rate can move. If the rate changes after the initial deal, the actual payment may differ from an estimate that assumes one rate throughout.

Why term length matters

A longer term spreads repayment across more months. That can reduce the monthly figure, but interest is charged for longer. Compare both the monthly payment and total repayment rather than choosing only the lowest monthly amount.

Fees and costs to budget separately

Possible costs include booking, arrangement or product fees, valuation, surveys, legal and conveyancing costs, insurance, moving costs and the relevant property transaction tax. If a lender allows a fee to be added to the loan, interest may then be charged on that fee.

How to use an estimate responsibly

1. Enter the loan amount rather than the property price.
2. Use the rate from the relevant mortgage illustration.
3. Test a higher future rate.
4. Compare total interest across several terms.
5. Check the lender’s official illustration before committing.

Independent guidance: MoneyHelper mortgage calculators and explanations and mortgage fees and buying costs. This guide is general information, not mortgage or financial advice.