Can I afford the scheduled payment? Use the repayment calculator, then repeat it at a higher rate.
Could overpaying shorten the mortgage? Use the overpayment calculator after checking your lender's allowance and charges.
Should spare cash reduce debt or remain accessible? Compare overpaying with saving using an after-tax savings assumption.
Would a new deal recover its costs? Use the remortgage and fee-comparison tools with every unavoidable fee.

The four figures to verify first

Take the outstanding balance and remaining term from a recent mortgage statement, the applicable rate from the lender's notice, and product or exit fees from the written terms. A precise calculation based on the original loan or an expired rate is still misleading.

Stress-test rather than predict

Run more than one plausible rate and time period. The site does not forecast interest rates, property values, eligibility or lender decisions; it helps expose how an assumption changes an illustration.

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.

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.