About Mortgage Extra Payment

Mortgage Extra Payment (mortgageextrapayment.com) is a free, independent set of calculators built for one purpose: to show homeowners and prospective buyers exactly how much interest and time they can save by paying extra toward their mortgage — with numbers they can actually trust.

Why we built this

Most online mortgage calculators are built for a single market and quietly get the math wrong for anyone else. A US-style calculator applied to a Canadian mortgage, for example, ignores the legally required semi-annual compounding rule and overstates or understates real savings. We built Mortgage Extra Payment to handle the US, UK, Canada and Australia correctly, using the interest-compounding convention and prepayment norms that actually apply in each country.

How our calculations work

Every result on this site is generated from a standard amortization formula, applied month-by-month against your actual loan balance — the same underlying method mortgage servicers use internally. Extra payments (monthly, one-time, annual, or accelerated bi-weekly) are applied directly to principal in the month you specify, and interest for every subsequent month is recalculated on the reduced balance. Our full calculation methodology, formulas and assumptions are documented in detail, and our editorial policy explains how we research and review our guides.

What we are not

We are not a lender, mortgage broker, bank, or financial advisory firm. We do not collect loan applications, and we never ask for personally identifiable financial account information. The figures produced by our calculators are estimates for educational purposes and should be confirmed with your mortgage lender or a licensed financial advisor before you make a financial decision — see our Financial Disclaimer for details.

Questions or feedback?

If you spot a calculation that looks off, or have a suggestion for a new calculator, we'd like to hear about it — visit our Contact page.