UK mortgage calculators

Interest-Only vs Repayment Calculator

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What this result means

Interest-only payments cover modelled interest but do not repay the original capital. A credible repayment strategy for the full balance is therefore central to the decision.

How to use the calculator well

Enter the full loan balance and current rate.
Compare the interest-only payment with a repayment mortgage over the same term.
Identify how the capital would be repaid and test that strategy separately.

Worked scenario

At 5%, interest on £200,000 is approximately £833.33 per month before fees, while the capital remains £200,000. The lower monthly payment is not the total cost of becoming mortgage-free.

Questions people ask

Will selling the property repay the loan?

That depends on the future sale value, costs and lender requirements; property prices can fall.

Can I switch to repayment later?

Possibly, but it can require lender approval and higher payments over a shorter remaining term.

Sources and review standard

Calculations are independently implemented illustrations and were reviewed on 4 September 2026. We check factual boundaries against MoneyHelper's mortgage cost guidance, FCA consumer mortgage information and relevant lender documentation. Rates and product terms are never presented as live offers.

Before relying on this estimate

This is an educational illustration, not mortgage, financial, tax or legal advice, a lender decision or an offer. Exact rates, fees, early-repayment charges and product rules can materially change the result.

Check the figures with your lender, broker or qualified adviser. Your home may be repossessed if you do not keep up repayments on your mortgage.

Editorial responsibility

Published by Acerville Sparks Limited. Software assists research, drafting and automated formula testing. Primary sources, assumptions and limitations are shown so readers can inspect the work. No independent mortgage professional or financial adviser review is claimed. Reviewed 4 September 2026.