Calculator
Polish mortgage overpayment calculator
Explore how one-off and regular overpayments affect a fixed-rate, equal-payment loan. Choose a shorter term or lower instalments. Inspect monthly balances, interest and savings after the fees you enter.
Calculator
Enter data
Enter remaining principal, a fixed rate and term. Use fees from your own agreement. Fields marked with an asterisk are required.
How to use the calculator
- The one-off overpayment happens now, before the next interest period, and may repay the whole balance. Recurring overpayments follow every instalment, starting in month one.
- Lower-payment mode recalculates after each overpayment over the remaining original term. Shorter-term mode retains the original payment. Enter only fees actually applicable to your agreement.
Calculation details
Formula and calculation method
Annuity instalment at annual rate/12. Each month: interest on balance rounded to cents, instalment, overpayment capped at remaining balance. Final payment closes the balance. Savings = baseline interest − new interest − fees.
Worked example
PLN 12,000 principal, 12 months and 0%: PLN 1,000 payments. A PLN 2,000 overpayment with a shorter term gives ten PLN 1,000 payments. Interest cannot fall below zero; fees result in negative savings.
Limitations
- Not a bank schedule: excludes daily dates, rate changes, insurance, payment holidays and declining-principal instalments. Every month is 1/12 year. Actual overpayment dates and amendment terms matter.
- The fee percentage applies to each actual overpayment; the fixed fee is charged once only if an overpayment occurs. The model does not determine whether fees are lawful or calculate statutory caps. The upfront overpayment is in the summary, outside the payment table.
Sources
Engine version: 1.0 · Last reviewed: 22 September 2026
Frequently asked questions
What does this tool cover?
Explore how one-off and regular overpayments affect a fixed-rate, equal-payment loan. Choose a shorter term or lower instalments. Inspect monthly balances, interest and savings after the fees you enter.
Which assumptions should I verify?
Not a bank schedule: excludes daily dates, rate changes, insurance, payment holidays and declining-principal instalments. Every month is 1/12 year. Actual overpayment dates and amendment terms matter. The fee percentage applies to each actual overpayment; the fixed fee is charged once only if an overpayment occurs. The model does not determine whether fees are lawful or calculate statutory caps. The upfront overpayment is in the summary, outside the payment table.
Are entered values stored?
Calculations run locally in your browser. Entered identifiers, amounts and results are not stored or sent to analytics.