What is WIBOR and why does it matter for a Polish mortgage?

WIBOR (Warsaw Interbank Offered Rate) is the reference rate Polish banks use to price variable-rate mortgages. The bank adds a fixed margin on top of WIBOR to set the total interest rate, so the payment moves whenever WIBOR is reset, typically every three or six months depending on the loan.

RRSO (Rzeczywista Roczna Stopa Oprocentowania) is the Polish equivalent of an annual percentage rate. It expresses the total cost of the loan, including one-time fees like the arrangement commission, as a single effective annual rate, so it is normally higher than the nominal WIBOR-plus-margin rate.

What is the difference between equal and decreasing installments?

With equal installments (raty rowne), the total monthly payment stays constant while the interest and principal split shifts over time. With decreasing installments (raty malejace), the principal portion is fixed every month, so the total payment is highest at the start and falls steadily as the balance drops.

Does this calculator use live WIBOR data?

No. WIBOR is published daily and varies by tenor (1M, 3M, 6M). Enter the current rate quoted by your bank or published by the reference administrator for the tenor your loan uses.

Is the RRSO estimate exact?

It is a simplified estimate based on the loan amount, arrangement fee, and payment schedule you enter. The official RRSO disclosed by a bank can also include mandatory insurance, account maintenance fees, and other charges that this calculator does not model, so treat the result as directional, not a substitute for the lender's disclosure.

Why does the WIBOR benchmark matter beyond just this calculator?

Poland has been transitioning parts of its financial system toward alternative reference rates, but WIBOR-plus-margin remains the standard structure quoted on most existing and new mortgage offers, which is why it is the input this calculator expects.

Poland Mortgage Calculator

Enter your property value, loan amount, WIBOR rate, bank margin, and term to get the monthly payment, amortization schedule, and an RRSO representative-rate estimate for a Polish mortgage.

Loan Details

Property Value (PLN)

Loan Amount (PLN)

WIBOR Rate (%/yr)

Bank Margin (%/yr)

Loan Term (years)

Installment Type

Arrangement Fee (% of loan) (optional)

One-time bank commission, used only to estimate the RRSO.

Enter loan details to see the payment, RRSO estimate, and amortization schedule.

First Monthly Payment

0 zl

interest + principal

Loan-to-Value

WIBOR + Margin

RRSO Estimate

Total Interest

0 zl

Year-by-Year Schedule

Year	Start Balance	Interest Paid	Principal Paid	Total Paid	End Balance

Summary

Most variable-rate mortgages in Poland are priced as a WIBOR reference rate plus a fixed bank margin, and lenders must disclose the RRSO, a representative annual rate that folds in one-time costs like the arrangement commission alongside the interest itself. Polish borrowers can also choose between equal installments, where the payment stays flat and the interest-to-principal mix shifts over time, and decreasing installments, where the principal portion stays fixed and the total payment falls every month. This calculator builds a month-by-month schedule for either installment type and estimates the RRSO from the WIBOR-plus-margin rate and an optional arrangement fee.

How it works

Enter the property value and the loan amount to establish the loan-to-value ratio.
Enter the current WIBOR reference rate and the bank margin charged on top of it.
Enter the loan term in years and choose equal installments or decreasing installments.
Optionally enter a one-time arrangement fee (commission), which is factored into the RRSO estimate.
The calculator builds a full monthly schedule, then aggregates it into a year-by-year interest, principal, and balance breakdown.
The RRSO estimate solves for the effective annual rate implied by the net amount financed after the arrangement fee, not just the nominal WIBOR-plus-margin rate.

Use cases

Estimating the monthly cost of a WIBOR-based variable-rate mortgage before applying.
Comparing the payment pattern of equal installments against decreasing installments on the same loan.
Seeing how a higher or lower bank margin changes the total interest paid over the loan term.
Checking how an arrangement fee affects the RRSO compared to the nominal interest rate.
Planning a household budget around the first-year monthly payment and the declining balance.
Understanding how much of an early payment goes to interest versus principal under each installment type.

Frequently Asked Questions

Last updated: 2026-09-09 · Reviewed by Nham Vu