Decision planning calculator
Mortgage Overpayment Calculator
Estimate the time and interest saved by a mortgage lump sum, monthly overpayment, or both.
Debt and borrowing decisions →Reviewed by Syvoq Editorial Team ·
Model the loan, then protect the household that still has to live with it
Use the current mortgage balance, current rate, and remaining term—not the figures from the original offer. Enter the lender’s present early-repayment charge and ask whether an overpayment reduces the term or the instalment. This model keeps the scheduled payment unchanged after reducing principal, so the estimated benefit appears mainly as a shorter term and lower future interest.
Before using the result, remove money needed for bills, taxes, known repairs, and an appropriate emergency reserve. Interest savings may be relatively certain, but the payment is difficult to reverse. A household that must borrow on a card after the next repair can lose the financial benefit of an overpayment that was mathematically attractive in isolation.
A real-world check
A modest lump sum plus a repeatable monthly extra
A borrower with €180,000 remaining over 25 years at 3.5% tests a €5,000 lump sum and €150 extra each month. The calculator includes a 0.5% charge on the lump sum and shows both time and interest saved, allowing the borrower to compare the benefit with the cash reserve being surrendered.
How to read the result
Net savings are meaningful
Confirm the lender illustration and verify that the remaining cash still covers likely household shocks.
The charge absorbs much of the benefit
Compare a smaller payment, a later date, or recurring extras allowed under the contract.
Time saved matters most
Keep the original scheduled payment after overpaying if the lender permits and the monthly budget supports it.
What this calculator cannot know
- The model assumes a constant interest rate and immediate principal reduction; variable rates and lender recalculation rules will change actual results.
- It excludes insurance, account packages, tax effects, refinancing options, opportunity cost, and the value of keeping cash accessible.
What to do next
- Request a current written overpayment illustration from the lender.
- Run the result again with a higher interest rate and a smaller overpayment.
- Keep the emergency reserve and known near-term costs outside the amount considered.
See the whole plan
Track the house goal without losing sight of everything else
Keep the deposit, cash reserve, debt, and monthly budget visible in the same financial picture.
Common questions
About this calculator
Will my lender reduce the term or the monthly payment?
That depends on the contract and lender process. This calculator assumes the normal payment continues, which shortens the term. Confirm how your lender applies an overpayment.
Does Portugal charge a fee for mortgage overpayments?
A charge may apply and rules or temporary exemptions can change. Enter the current rate from your contract or lender quote instead of relying on a generic default.
Should I use savings to overpay the mortgage?
Compare interest saved with the value of liquidity. Protect near-term bills and an appropriate emergency reserve before making an irreversible payment.
How it works
The scheduled payment uses a standard repayment-mortgage formula from the current balance, rate, and remaining term.
The lump sum reduces principal immediately; the original scheduled payment and monthly overpayment then amortize the lower balance.
Interest saved is compared with the original schedule, while the configurable lump-sum charge is shown separately.
Educational planning estimate. It does not replace an official calculation or individualized financial, tax, or legal advice.
Related calculators
Portugal Mortgage Calculator
Estimate a mortgage payment for a Portugal property purchase, including down payment and monthly ownership costs.
Open calculatorLoan Repayment Calculator
Estimate monthly loan payments, total interest, and the payoff impact of extra payments.
Open calculatorHouse Deposit Goal Calculator
Combine the intended deposit, buying costs, current savings, and deadline into one house-fund target.
Open calculator