Investment approach
Euribor and mortgage payments: reading the formula in a bank offer
The 12-month Euribor was 3.247% in September 2026. How the index feeds into the payment, what the bank must show before signing and how much the payment rose over a year in a worked example.
Euribor is the eurozone interbank rate to which a variable-rate mortgage in Spain is usually tied: the borrower's rate equals the index plus the bank's fixed spread. The official 12-month value for September 2026 was 3.247%, 1.075 percentage points above the figure a year earlier (Banco de España, 1 October 2026). At each review the payment is recalculated using the latest value.
Where the official Euribor value comes from
Euribor is calculated and published by the European Money Markets Institute (EMMI). For mortgage contracts in Spain the official reference rate is used: the arithmetic mean of the daily Euribor values over the month, which the Banco de España publishes by repeating EMMI's calculation (Banco de España, Cliente Bancario).
The list of official rates is wider: it includes Euribor for one week, one month, three and six months, government bond yields and the five-year IRS. But in residential mortgages the 12-month Euribor is the most common, as the Banco de España itself notes on the same page.
The ECB does not set Euribor, but its decisions shift the cost of money for banks. Since 16 September 2026 the ECB deposit rate has been 2.50% after a rise of 0.25 percentage points (ECB).
| Month | 12-month Euribor, official value |
|---|---|
| September 2025 | 2.172% |
| March 2026 | 2.565% |
| July 2026 | 2.855% |
| August 2026 | 2.954% |
| September 2026 | 3.247% |
Source: press release archive on the Banco de España statistics page, accessed on 13 October 2026.
How Euribor gets into your payment
The rate on a variable-rate mortgage is made up of three elements, and all three are written in the contract: the index, the spread and the review frequency. On the review date the bank takes the index value specified in the contract, adds the spread and recalculates the payment on the remaining debt and term.
Hence a practical rule: comparing offers by today's rate is pointless. What gets compared is the spread, the review frequency (every 6 or 12 months) and which month of the index is used for the recalculation. The payment changes not when news about Euribor appears, but only on the review date.
The law limits what a bank may write into the formula. The index must be objective, verifiable and independent of the lender itself; a floor on the rate (cláusula suelo) is prohibited in a variable-rate mortgage; the interest rate cannot become negative (art. 21 Ley 5/2019).
How much the payment changed in a year: a worked example
Worked example, not a forecast. Outstanding debt of 300,000 €, remaining term of 25 years, spread of 0.80%, annual review using the September value. The payment is calculated as an annuity over the remaining term.
| Review scenario | Euribor | Borrower's rate | Monthly payment |
|---|---|---|---|
| Review in autumn 2025 | 2.172% | 2.972% | about 1,418 € |
| Review in autumn 2026 | 3.247% | 4.047% | about 1,591 € |
| Stress: index another 1 percentage point higher | 4.247% | 5.047% | about 1,762 € |
The index rise of 1.075 percentage points over the year added about 173 € a month in this example, roughly 2,080 € a year. Another percentage point would add about 171 € a month. The figures depend on the amount, term and spread, so it is more useful to calculate your own case in the calculator than to carry the example over to yourself.
What the bank must show before signing
Before signing, the bank or intermediary must hand over a package of documents at least ten calendar days in advance (art. 14 Ley 5/2019). For a variable rate the package includes a separate document with payments under different scenarios of rate changes. That is a ready-made stress test, and it is worth reading before the advertised rate.
What the package contains:
- FEIN (Ficha Europea de Información Normalizada), the standard European information sheet. It is treated as the bank's binding offer before signing, for at least ten days.
- FiAE (Ficha de Advertencias Estandarizadas), the warnings sheet: which official index is used, whether there are limits on the rate, the consequences of late payment, the allocation of costs.
- A document with payment scenarios for the variable rate.
- The draft contract with a breakdown of all costs.
The same law allocates the arrangement costs: the tasación (valuation) is paid by the borrower; the gestoría (paperwork agent), the notary's fee for the loan escritura (deed) and the registration of the security are paid by the bank (art. 14.1.e). That helps compare the real cost of two offers.
Which terms to compare in two offers
The formula is compared as a whole, not the figure on the first page. Besides the spread, look at:
- whether the rate has a fixed first period and how long it lasts;
- whether the spread falls if you take out insurance or open a payroll account, and what happens if you give up those products;
- fees for early repayment and for switching to a fixed rate;
- the TAE (the annual equivalent rate, Spain's APR). For a variable rate it is calculated on the assumption that the rate does not change, so the FEIN shows another, illustrative TAE with a marked rise in the rate (art. 8 Ley 5/2019).
How current rates affect the Barcelona market as a whole is covered in the article on Euribor and mortgages in the market. If the loan is needed for a project with renovation and resale, the logic is different: see the analysis of variable and fixed rates for a project.
When a variable rate does not suit
A variable rate suits poorly if the budget cannot withstand the stress scenario in the bank's document. That applies to a buyer whose payment is already close to the limit of their income, who has other mandatory payments or income in another currency, so exchange rate swings add to the swings in Euribor.
It also does not suit someone who plans to hold the loan for many years and values predictability above the starting rate. Then the honest course is to compare the fixed and mixed rates by full cost, with a broker or with several banks: on choosing an intermediary see the article broker or bank directly.
Questions and answers
What is Euribor in simple terms?
It is the rate at which eurozone banks lend to each other. In Spain many variable-rate mortgages are tied to its 12-month monthly average: if the index rises, the payment rises at the next review.
Where can I see the official Euribor for the month?
On the Banco de España's interest rate statistics page, where a press release with the value comes out every month. For the contract, what matters is precisely the official monthly average, not the daily value on financial websites.
Can a bank set a minimum rate on a variable-rate mortgage?
No. Ley 5/2019 prohibits a floor on the rate in variable-rate loans, and the interest cannot be negative even with a negative index.
How often does the payment change because of Euribor?
As often as the contract says, usually every 6 or 12 months. Between review dates the payment does not change, whatever the news about the index.
How much will the payment rise if Euribor goes up by 1%?
It depends on the outstanding debt and the term. In the worked example with a debt of 300,000 € over 25 years, a rise of one point adds about 170 € a month. The bank must show its own scenario in a separate document before signing.
