Mortgage Repayment Calculator

How this calculator works

This browser-based tool helps you make a first, transparent estimate from the values you provide. Enter the figures in the fields and the result updates as you edit them. JavaScript performs the calculation on your device; the calculator does not send your salary, property, vehicle or account details to a calculation server. Keep supporting documents secure and only enter sensitive figures on a device you trust.

Formula, assumptions and limits

Estimate a mortgage instalment and indicative payoff time. The annuity is a mathematical estimate. Contract terms and section 488 BGB govern the actual loan.

Do not rely on a rounded estimate for a tax return, payment or legal decision. Compare it with official notices, current rate tables and professional advice where needed. Real-world outcomes may include additional reliefs, fees, rate changes or personal circumstances that a simple calculator cannot represent. Your entries are not saved and are discarded when you close the tab.

Use the output as a planning aid: verify each input, read the assumptions and adjust the figures when your circumstances differ. If an important detail is uncertain, contact the relevant authority or a qualified tax, legal or financial professional.

Before acting, check your inputs, tax year and jurisdiction. Note the assumptions used, compare the result with records and official guidance, and recalculate when rules or your circumstances change.

Understanding the annuity, interest and remaining balance

With a standard annuity mortgage, the agreed payment usually stays level during a fixed-rate period. Each payment reduces the balance, so the interest portion tends to fall and the repayment portion tends to rise. This estimate approximates the monthly payment by multiplying the loan by the annual borrowing rate plus the initial repayment rate, then dividing by twelve. Its indicative payoff time assumes the same inputs continue until the balance is cleared. Enter both rates as annual percentages and compare scenarios using the same loan amount so that changes are meaningful.

A real mortgage may include a fixed-rate term, arrangement fees, an initial drawdown date, overpayments, payment holidays, repayment changes and a new interest rate after the fixed term. These can materially change the balance and total interest. A lower initial repayment can make the monthly amount easier but leave more debt when the fixed period ends. The output is not a full amortisation schedule: it does not model every payment date or rounding convention. Ask lenders for the monthly payment, effective annual rate and projected balance at the end of the fixed period. Keep room in the budget for repairs and rate changes. Use this estimate to compare options, not as a loan offer or affordability decision.

Frequently asked questions