UK mortgage calculators
About MortgageCalcs
Why MortgageCalcs exists
MortgageCalcs turns common mortgage questions into transparent illustrations. It shows the inputs, calculation and limitations so visitors can challenge a result instead of accepting an unexplained number.
Who produces it
The site is operated by Acerville Sparks Limited. Calculator formulae are covered by automated examples and reviewed against authoritative consumer and regulatory material. We are not a lender, broker or financial adviser and receive no payment for presenting a particular result.
How content is reviewed
Dated assumptions are checked when rules or source material change. Material corrections are applied across the calculator, explanation and test example together. Contact us if you believe a result or explanation is wrong.
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.
Calculation and review method
Each calculator has a named mathematical function, independently calculated examples and failure tests for invalid inputs. A production build must retain the formula explanation, worked scenario, source boundary and prominent warning. Changes to a formula and its tests are reviewed together.
Who, how and why
Acerville Sparks Limited publishes MortgageCalcs to make common mortgage comparisons inspectable rather than to recommend a product. Software assists calculation, testing and drafting; the visible assumptions, authoritative references and limitations allow a visitor to verify the result.
Commercial boundary
No lender pays to alter a formula or conclusion, and the site does not currently rank mortgage products. Any future advertising or referral relationship must be labelled and kept outside calculation controls and results.
Last substantive review
The public calculators, examples and consumer boundaries were reviewed on 4 September 2026. Time-sensitive rates and lender terms are intentionally supplied by the visitor rather than presented as current market facts.
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.