Calculator
Borrowing capacity — household budget estimator
How much financing fits your chosen payment budget? This model subtracts living costs, obligations and a reserve, then limits the new payment using your chosen share of total debt payments in income. It compares financing at the base rate and entered rate increase. No default is a current offer or universal bank rule.
Calculator
Enter data
Household PLN budget, chosen debt-payment share, nominal rate, percentage-point buffer and term. Fields marked with an asterisk are required.
How to use the calculator
- Replace all examples with stable net income and complete expenses. The reserve is additional; do not count it again in living costs.
- Enter your chosen maximum total debt-payment share. The smaller constraint applies: budget surplus or remaining share allowance. No payment room yields a model amount of zero.
- Choose nominal rate, term and a percentage-point increase. 6% + 2 points means 8%, not 6.12%. Compare scenarios and obtain the actual assessment from a bank.
Calculation details
Formula and calculation method
Payment budget = max(0, min(income − costs − existing payments − reserve, income × chosen share − existing payments)). Principal = payment × [1 − (1 + r)^(-n)] / r, where r = stressed annual rate / 1200. At 0%, principal = payment × n; principal is rounded down to cents.
Worked example
Example: PLN 10,000 income, PLN 4,000 costs, PLN 1,000 existing payments, PLN 1,000 reserve and a chosen 40% share. Surplus is PLN 4,000 but debt-share room is only PLN 3,000. At 0%, zero rate buffer and 120 months, the model amount is PLN 360,000.
Limitations
- A budget model, not a full bank creditworthiness assessment. No BIK, scoring, age, contract type, income verification, minimum household costs or bank-specific card/limit/guarantee treatment.
- PLN, equal monthly payments, one constant rate per scenario and 1–360 months. No commissions, insurance, fees, down payment, LTV or rate changes during repayment. Not APR/RRSO, a recommended debt level or a guaranteed maximum amount.
- Entered debt share and buffer are user assumptions. Bank buffers and assessment horizons under Recommendation S are not reproduced. The amount excludes schedule-rounding corrections; review the complete bank offer and conditions before borrowing.
Sources
- KNF — Recommendation S, June 2023, recommendations 8–9 (context, not a bank algorithm)
- UOKiK — mortgage payments, interest rates and simulation limitations
Engine version: 1.0.0 · Last reviewed: 30 September 2026
Frequently asked questions
Will a bank lend me the displayed amount?
Not necessarily. A bank checks income, costs, credit history, collateral and its own assessment rules. This result is only a mathematical household-budget scenario.
Are 40% and 2 percentage points mandatory?
No. They are explicitly illustrative, editable inputs—not a universal limit or current KNF buffer.
Are my financial inputs saved?
No. Entered figures and results stay in your browser. They are not added to the URL, persistent storage or analytics. Copying and printing are your choice.