Editorial Policy and Methodology

This page explains how Mortgage Savings Calculator produces its calculator results and its guides, and what they can and cannot tell you.

Who publishes this site

The site is published by Marble Cage Limited, trading as Mortgage Savings Calculator. See the About page and our affiliate disclosure.

What our content is, and is not

Our calculator and guides are general information for UK homeowners. We do not offer mortgage, financial, legal or tax advice, and nothing on the site is a personal recommendation. Always check your mortgage offer and terms, and consider speaking to a regulated mortgage adviser before you make a decision.

How the calculator produces its figures

• It models a standard UK capital-and-interest repayment mortgage.
• Interest is charged monthly at the annual rate divided by 12, rounded to the penny. Some lenders calculate interest daily, so your lender’s figures may differ slightly.
• Your contractual monthly payment is the level payment that would repay your balance over your remaining term.
• Overpayments start with your next payment and continue every month. The headline result keeps your payment the same, so the mortgage ends sooner. The “lower your payment” view assumes your lender recalculates your payment after each overpayment over the term left. Lenders differ, and some only do this on request.
• You can add one optional lump sum, paid with the payment for the month you choose.
• The interest rate is assumed to stay the same for the whole remaining term.
• The calculator applies no fees, early repayment charges or lender terms to its numbers. It shows a badge that compares your overpayments with a typical 10% yearly allowance, but the badge never changes a figure.
• Totals are added up in pence and shown rounded to whole pounds.

Results are estimates for planning, not offers or forecasts.

How figures in our guides are produced

Where a guide shows calculated figures, they come from the same calculator, with the inputs and assumptions stated next to them, so you can reproduce them in the free mortgage overpayment calculator. Some guides use simple round-number illustrations rather than calculator output.

Sources

We prefer primary sources: your lender’s own documents for lender-specific rules, and public guidance such as MoneyHelper and the Financial Conduct Authority for general information. Our pages about named lenders quote the lender’s own words next to our summary, link to the lender’s page, and show the date we checked it. An automated check reads each lender’s page every week. If every passage we quote is still on it, the “checked on” date is moved forward; if a passage has gone, the date is not moved and the page is flagged for us to read and update. The check confirms that the wording we quote is still there. It cannot detect changes elsewhere on a lender’s page, which is why each lender page tells you to check your own mortgage offer. The build also fails if a lender page has not been successfully re-checked in six months.

Dates on our guides

Guides show when they were published and, where the text has changed since, when they were last edited. “Last edited” means the text or figures changed on that date. It is not a statement that every fact was re-verified on that date, and lender rules and charges can change after it.

Corrections

If you find something that looks wrong or out of date, tell us through the contact page. When we confirm an error we correct it and update the “last updated” date.

Limits

Mortgage rules and charges vary by lender and product, and they change. Our figures do not know your lender’s terms, so check your mortgage offer or ask your lender before you overpay.