Mortgage calculator
The mortgage calculator works out the monthly payment and the amortization schedule of a fixed or variable mortgage, what an early repayment saves, and your share if you own the home with someone else. It is for anyone who wants to see how the French system adds up, including for a joint mortgage. Everything is calculated on this page.
How the payment is calculated
Spanish mortgages normally use the French system: the same payment every month, of which a growing part repays the loan and a shrinking part pays interest. With a loan P, a monthly rate i (the annual rate divided by 12) and n monthly payments:
Each month, the interest is the outstanding balance times i, and the rest of the payment reduces the balance. All the amounts are kept in whole cents, and the rounding left over goes into the last payment, so the principal repaid always adds up to the loan. (Why cents and not decimals: Why money should never be a float.)
Variable rates: Euribor plus a spread
A variable mortgage usually starts with a fixed rate for a few months, then adds the spread (the diferencial, fixed in your contract) to the Euribor at each review. At a review, the bank recalculates the payment for the balance and the months that are left, keeping the end date. If Euribor plus the spread falls below zero, the rate is zero: Spanish mortgage deeds say so, and the bank never pays you interest.
The three scenarios keep Euribor constant from the first review onwards. That is a simplification on purpose: nobody can tell you where Euribor will be in five years, and the useful question is how much a point up or down would change what you pay. With a constant Euribor, reviewing every 6 or 12 months gives the same result.
Early repayment: lower payment or shorter term
Paying off part of the loan early reduces the balance on which interest is charged. The bank then either keeps the end date and lowers the payment, or keeps the payment and brings the end date forward. Keeping the payment saves more interest, because the balance falls faster; lowering it leaves more money free each month. The calculator shows both. It doesn't include the early-repayment fee your contract may set.
Only the interest is an expense
Of each payment, the part that repays principal isn't spent: it moves from your bank account into the home you own. Only the interest is a cost. That is how Ahorreo counts a mortgage, and it is why the schedule above keeps the two apart.
Your share of a joint mortgage
If you own the home with someone else, your share of the debt, the payment and the interest is usually your ownership percentage. The figures under each total show that share. We wrote about why it matters for net worth in Household or my share?
Frequently asked questions
How is the monthly payment calculated?
With the French system most Spanish mortgages use: the same payment every month, of which a growing part repays the loan. For a loan P, a monthly rate i and n payments, payment = P · i / (1 − (1 + i)−n). All amounts are kept in whole cents, and the rounding left over goes into the last payment.
How do the Euribor scenarios work?
A variable mortgage adds the spread fixed in your contract to the Euribor at each review. The three scenarios (low, central and high) keep Euribor constant from the first review onwards, which is a deliberate simplification: nobody can tell you where Euribor will be in five years, and the useful question is how much a point up or down would change what you pay. If Euribor plus the spread falls below zero, the rate is zero.
What does an early repayment change?
It reduces the balance on which interest is charged. The bank then either keeps the end date and lowers the payment, or keeps the payment and brings the end date forward. The calculator shows both. It doesn't include the early-repayment fee your contract may set.
How does my share of a joint mortgage work?
If you own the home with someone else, your share of the debt, the payment and the interest is usually your ownership percentage. The figures under each total show that share.
Is this financial advice?
No. It is for illustration only: your bank's figures depend on its own rounding, fees and payment dates. Everything is calculated on the page and nothing you type is sent anywhere.