How this works
This calculator estimates your mortgage borrowing capacity from Banco de Portugal’s two rules: the debt-service ratio (DSTI), which caps the payments of all your loans at 50% of net income, and the LTV cap, which sets how much of the property the bank finances (90% for your own permanent home, 80% otherwise). We also apply the regulator’s interest-rate stress test. Everything runs in your browser — nothing is sent anywhere.
- 1
Maximum payment (DSTI)
The debt-service ratio (DSTI) recommended by Banco de Portugal caps the payments of all your loans at 50% of net income. We subtract the payments you already have: maximum payment = income × 50% − existing debts.
- 2
Interest-rate stress test
Banks must check you could withstand a rate rise. To the contract rate we add the increment from Instrução 3/2018: +0.5 pp up to 5 years, +1 pp between 5 and 10 years and +1.5 pp above 10 years. The loan is sized at that stressed rate.
- 3
Maximum principal
Inverting the payment formula, the principal that payment can service is P = payment × (1 − (1+i)⁻ⁿ) / i, where i is the monthly rate (stressed rate ÷ 12) and n the number of months (years × 12).
- 4
LTV cap and property price
The loan cannot exceed 90% of the property value for your own permanent home, or 80% for other purposes, on the lower of price and appraisal. From this we get the maximum property price = principal ÷ LTV and the minimum down payment you need.
- 5
Putting it together
The approvable loan is the smaller of the DSTI limit and the LTV limit. If you enter a property price, we tell you whether it is within your capacity and the down payment that purchase would need.
Frequently asked
What is the debt-service ratio (DSTI)?
It is the weight of the payments on all your loans — mortgage, car, cards, personal credit — in your income after tax and social security. Banco de Portugal recommends it stays at or below 50%. So the debts you already carry directly reduce the payment available for a new mortgage.
Can the bank lend more than this shows?
It can. The recommendation follows a "comply or explain" rule: each bank may grant up to 20% of a year’s credit to borrowers with DSTI up to 60%, and up to 5% beyond the limits. A second earner also raises household income and with it your capacity. This tool shows the standard 50% scenario; your bank may go somewhat further.
Why do the term and rate change the result so much?
A longer term means a smaller payment for the same principal — so more principal fits inside the 50% and your capacity rises (though you pay more interest overall). The rate does the opposite: higher rate, bigger payment, less principal supported. The stress test adds a further 0.5 to 1.5 points to the rate, deliberately lowering capacity for prudence.
What is the LTV cap and the down payment?
LTV (loan-to-value) is the share of the property the bank finances: up to 90% for your own permanent home, up to 80% otherwise. The rest is the down payment you must provide — 10% or 20%. The ratio is taken on the lower of price and the bank’s appraisal, so if the appraisal comes in below the price you may need a bigger down payment.
Does this guarantee the bank will approve me?
No. It estimates capacity against the regulator’s limits. The bank also weighs your credit history and scoring, job stability, contract type, your age (which limits the term and, past 70, triggers an income cut in the calculation) and the cost of required insurance. Use this to orient yourself before talking to the bank.
DISCLAIMER
An estimate for orientation, based on the limits recommended by Banco de Portugal (50% DSTI and 90%/80% LTV) and the stress test in Instrução 3/2018. Banco de Portugal has announced a cut in the DSTI limit from 50% to 45%, expected to take effect in the second half of 2026; until it is in force this tool applies 50%. The recommendation follows a «comply or explain» rule, so a bank may lend outside these limits for part of its output. It excludes required insurance, fees and the APRC (TAEG), and does not consider credit scoring, credit history, contract type, age-based maturity limits or the income cut applied to terms extending past age 70. LTV uses the lower of price and appraisal. Not financial advice.