Methodology

Scope

This website is only about the Spanish mortgage market. The laws, taxes and banking practice we explain are those of Spain. The calculators are for guidance and do not replace the information your bank gives you or professional advice.

Mortgage calculator

• French amortization system: constant payment. Each month the interest is the outstanding capital times the monthly rate (the annual rate divided by 12); the rest of the payment repays capital.
• Monthly recalculation: the payment is recalculated each month from the outstanding capital and the months left. On a fixed rate this gives the same payment every time; on a variable rate it allows the rate to change in any month.
• Variable mortgage: the rate is Euribor plus the spread. The Euribor entered is used for the first 12 months and the "future Euribor" from month 13. It is an assumption about how it will move, not a forecast.
• Taxes and purchase costs: calculated as a percentage of the price that the user enters. We do not look up the rates of any community.
• Not included: insurance, fees, tied products or other products.

Early repayment calculator

• The current payment and the total interest that would be left to pay without repaying are calculated.
• Lower the payment: with the reduced capital and the same term, the new payment and the remaining interest are calculated.
• Shorten the term: the payment stays and we calculate how many months are needed to clear the reduced capital; the last payment is smaller.
• Saving: the difference in interest minus the fee, which is calculated on the amount repaid. A constant rate is assumed for the remaining term.
• Maximum legal fee: values from article 23 of Law 5/2019: variable, 0.25% in the first 3 years or 0.15% in the first 5; fixed, 2% in the first 10 years and 1.5% afterwards. We checked them against the consolidated text of the BOE (the Spanish official gazette) on 9 October 2026.

How we check that it matches the app

The web calculators use the same calculation engine as the Hipoteca Clara app. Before publishing any change, a set of automated tests runs the app's own code and the website's code on hundreds of combinations of data, and requires payments, interest and every row of the schedule to match.

Sources and review

• Law 5/2019 on real estate credit agreements, BOE (in Spanish).
• Portal del Cliente Bancario, Bank of Spain (in Spanish).

We review the content when the rules we cite change and at least once a year. Last reviewed: 9 October 2026.

Contact

If you find a mistake or want to make a suggestion, write to aidoapps@aidomedia.com. See also the legal notice.