Debt reducer

Mortgage Calculator

Check how much interest and time you could save with an extra monthly repayment.

SIMULATOR

Your numbers

Recalculates instantly as you move the sliders.

ESTIMATED RESULT€14,867
YEARS REDUCED3.7 years
INTEREST WITH EXTRA€75,470
MONTHLY PAYMENT€901
Current-plan interest€90,337
Interest with extra€75,470
Estimated saving€14,867

Compare total interest: the larger the difference, the greater the saving from repaying earlier.

Save my saving of €14,867. With €100 extra per month you would save interest and shorten the debt.

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What it solves

This calculator estimates how much interest and time you may save by adding an extra monthly payment to a mortgage, comparing schedules with and without the extra payment.

How to use it

Enter the outstanding principal, interest rate, remaining term and extra monthly amount. The tool estimates the payment, total interest and months shortened.

How it is calculated

It calculates the standard French amortization payment and then applies the extra amount to principal each month. Lower principal reduces future interest.

Worked example

Adding $100 per month to a typical mortgage can save around $9,000 in interest and shorten the loan by several years, depending on principal, rate and term.

How to interpret it

Mortgage overpayment has a known effect: each dollar repaid avoids interest at the mortgage rate. Compare that with other possible uses of the money, including risk, liquidity and taxes.

Common mistakes

Avoid overpaying until the emergency buffer disappears. Also check whether the mortgage charges early-repayment fees.

Assumptions

Assumptions: fixed interest rate and extra payments used to shorten the term. Variable-rate mortgages and fees can change the real result.

Sources

Bank of Spain — Client Banking Portal (mortgages) · CNMV — Investor Education.

Learn the context

Understand Mortgage Calculator better

Pair the simulation with a clear explanation, examples, and limits before using the result as educational context.

Read the guide

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Frequently asked questions

Mortgage Calculator, with context

Reduce payment or term?

Reducing term usually saves more interest; reducing payment improves monthly cash flow.

When does overpayment save more?

Earlier in the mortgage, because outstanding principal is higher.

Can there be fees?

Yes. Check your mortgage deed.

Overpay or invest?

It depends on the mortgage rate, liquidity needs and risk tolerance. The decision is yours.

Illustrative results for educational purposes · Educational information, not financial advice.